Reposting here for completeness in this thread:
OK, here it is, please tell me if something needs a better description or correction.
Here's how I'd do it if I had to do it again and I wanted to minimize the welder's time...
Step 0: Before you start, get some (preferably stainless steel) U-bolts that match the holes in the vertical flat of the tank guard's bottom mount. I ended up using M6 x 24mm x 40mm (diagram below) found at the following link: https://www.amazon.com/gp/product/B07HKBSLYD/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1
Note: Don't just order what I ordered. Measure the holes in the vertical flat of YOUR tank guard's bottom mount. Ideally, you should use a U-bolt that does not require modifying the holes. I modified my holes during an earlier attempt, so I don't know the original distance between the holes. The threaded bolt ends of the U-bolt below are 24+3+3=30mm from center to center; if the holes on the vertical flat of your bottom mount are the same from center to center, then this u-bolt should be perfect. If you can't get U-bolts that match the holes, you'll need to either bend the U-bolt a bit (OK if it's just a little) or you'll need to modify your holes to match the U-bolts you get. Of course, you need flat washers large enough to cover the holes in the vertical flat of the bottom mounts and I recommend you use lock nuts, everything stainless steel if possible. I actually used double lock nuts and orange thread lock for triple redundancy.
Step 1: Mount the Rally Raid engine guard per their instructions.
Step 2: Mount the Wunderlich tank guards (one side, then the other, inserting them together at the top) using the top mounting spacers, washers, and bolts per their instructions (includes moving the horn); cable-tie the bottom mount tightly to the engine guard. This step was the hardest for me because it's hard to see up under the upper fender and hard to do by feel.
Step 3: Optional/Recommended: With #2 complete, make sure the tank guard upper mounting bolts are fully tightened and go visit your welder on/with the bike, show him how it looks now (where you have it cable tied) and show him pictures of what you want it to look like (selected from the ones I've posted); offer him these instructions. If he has a process he wants to follow to accomplish the job, do what he says and disregard the remainder of these instructions.
Step 4: Mark (I used a silver Sharpie) the tank guard where you need to cut the tube to remove the tank guard bottom mounts (below the radiator plastic; above the engine guard).
Step 5: Remove the tank guards from the bike and secure one side at a time in a vise using a circular rubber clamp or other cushioning so the tube isn't crushed and, using a hack saw or grinder cutting wheel, cut the tube as straight across as possible at the mark, thus removing the bottom mount.
Step 6a: If the cut is close to the horizontal flat of the bottom mount (as mine was on one side), grind the excess material off the horizontal flat, leaving the horizontal flat area clean and ready to have the tank guard tube re-welded to it.
Step 6b: If the cut isn't close to the horizontal flat of the bottom mount, leave it as-is.
Step 7: Reinstall the tank guards on the bike, using the top mounting spacers, washers, and bolts and loose cable-ties somewhere toward the bottom to hold the tank guard tubes roughly in position.
Step 8: Use your U-bolts to secure the vertical flat of each bottom mount to the engine guard. From my pictures, it's obvious that the horizontal flat offset points OUTWARD. Much more subtle, there is also a little REARWARD offset. Look closely at my pictures and you'll see it. As I recall, I actually ended up swapping the left and right bottom mounts to get the offset optimal in terms of clearing the radiator and gas tank plastics. Try each bottom mount on each side and decide how you want to do it. Once you decide, mark each bottom mount and each tank guard tube with an L for Left or an R for Right so you don't mix them up after removal. Hand tighten the U-bolts, leaving them loose enough that you can move the bottom mount around.
Step 9: Align the bottom mount horizontal flat with the horizontally cut tank guard tube above it. Ideally they should just touch (not everywhere, but more is better). If there is open space between these two, measure that distance and tell the welder so he can weld a spacer in between the two (or fill it during welding if its small enough). If the fit is too tight between these two, grind the excess material from the horizontal flat on the bottom mount if there is any and/or grind/cut some more material off the tank guard tube so the two pieces are just touching each other. In my case, we got the best fit by filling a little space with welding on the left side and removing a little material on the right side. Once everything fits, mark the tube and the horizontal flat in several places so the relative position of how you want them welded together is clear. Options: Hold the tube in position and draw a circle around it and/or draw several lines that start on the tube and turn horizontal on the horizontal flat of the bottom mount. Make sure you know which tube lines go with which horizontal flat lines by making them unique or numbering them. Before you remove them, double check you have both the bottom mounts and the tank guard tubes marked L or R.
Step 10: Optional/Recommended: Take just the tank guard pieces to the welder and have him tack weld them together as marked. Take them back to the bike and reinstall to double check that alignment is good.
Step 11: Once you're sure of the alignment, have the welder completely the weld each tank guard bottom mount completely to its corresponding tank guard tube. Once he's done, test the fit by fully installing the now welded tank guard.
Step 12: Last step is painting. A short test ride with the unpainted tank guard is OK, but don't go crazy; I did and rust quickly developed everywhere I had bare metal. This makes painting harder. I had access to a reasonably priced small scale powder coater, so I had them powder coated. Powder coating electrostatically pulls paint onto every part of the surface, even when there are nooks and crannies you can't see. If I did not have that access, I would have simply sanded everything smooth and used store bought spray cans of primer and the original black color to prime and spray paint all bare metal to match the original black color with at least two coats of the final color. Or just paint the whole thing whatever color you want to. (Note: Except red, I have that trademarked. I'm kidding; if you like red, go for it.) One comment from my powder coater: The Wunderlich powder coating is amazingly tough and durable; he had to chemically strip it before he could re-powder coat the whole thing. That did increase the cost to me. If you use spray paint, that won't matter.
Hope this helps.