It might be worth considering that 75/5s are getting quite valuable---unmolested ones that is. Rework the mirror holes and you hurt that value. You can make some very clean brackets that go forward from the existing mirror holes (tabs essentially) that will take any mirror you want. You just need one left handed bolt. Fifty cents from any of many fastener houses. And then there are the mirrors that come off the headlight bolts and a number of barends. I liked the barends because I had a clear view, no looking at your shoulder in half the mirror. I'm making a set of mirror stems for my RS because the factory mirrors are that bad (but look good). I'm destroying the existing mounts but new ones are only $18 a pair so I'll pick some up sometime and set them aside.