My experience with a rear rack weight limit that affected me the most is the cantilevering. You don't notice it much with heavier bikes or with longer wheelbases. Two bikes ago, I had a Vespa GTS300, comparable to the G310: 350lbs, 278cc. I had tried twice to design a rear rack wheelchair mount. I had a mount that was sturdy, but...on the test run, I discovered that it unweighted the front wheel. That's where most of the braking power is!
Long-term, I would make it part of my routine to regularly inspect the frame and bolts, but short-term is to make sure it doesn't mess with handling.
I plan on some long trips as well! My strategy is to try to keep the weight centered and low. Heavier things are going into the dry bag across the seat and the side cases. I plan on putting some smaller bags on the tank guards to offset the rearward weight. My rear rack luggage is usually dedicated to rain gear, day bag, and extra layers. On longer trips, I leave space in a topcase for food and drinks. It's no fun standing in a grocery store parking lot, sun going down, trying to figure out where to stash the things you got for dinner and/or breakfast.
