My old steel frame has about 128mm spread. I can squeeze 130mm
spaced hub in there, but I don't like doing it. I recently cracked my
right rear drop-out, and someone said that the spreading may have contributed.

So, if I reduce the spacing to 128mm on a Shimano 8 speed set-up, then have the
wheel dished accordingly, will this cause a problem?

I assume with the reduced spacing, the wheel must be dished to the right slightly more than
normal.

Any problems?