I did get the longer bolts to use the bar ends as well as the mirrors. I know they lengthen the whole width of the handlebars and filtering through traffic might present problems for some, but I live in a rural area so the width of the
bars does not affect me. As far as bolt length goes ,I don't think the standard,
original bolts will be long enough. On the other hand, if you bought the bolts from the link I provided and DID'NT use the bar ends, then the newly purchased 75mm x 8mm bolts would very likely be too long.
As for Blanking off the mirror stems, I used two rubber stoppers pushed flush into the threads and then got some black gloss paint I already had and painted over the rubber and the top of the aluminium mirror stems, to cover up the silver-bare aluminium which is exposed when you take the original mirrors off.