Richard,
I'm fortunate in that my FED5 has enough diopter correction that I can adjust it so I don't need to mash my glasses right up against the VF surround.
The FED2 I owned had some other issues for me so I didn't keep it long enough to sort out the eyeglass scratching.
What I have done on my Kiev4a is to go to my local hardware store and find a small rubber O-ring that would just fit around the VF surround. It also protrudes very slightly and so keeps my glasses from contacting the metal VF collar. I put a small amount of rubber cement to hold it in place a little more firmly than just friction.
You may be able to do something similar with the FED2(I can't recall the shape of the VF collar on that one). For the FED5, it may be better to find an O-ring that will fit on the VF surround instead of around it. And glue it in place. If you're good with an Xacto knife, you could cut a small ring out of leather or thin rubber and do the same thing.
I have seen self adhesive felt "dots"--intended for feet for small boxes and the like--if you find some in a good size, you could cut out the center, I'd think and then stick 'em on the VF. Probably not a permanent fix but they come in multiples and are fairly cheap.
I have seen commercial products for this situation but they are kind of pricey, I think.
Rob