steel-era downtube shifters on modern aluminum frame?
I picked up a Performance / Nashbar aluminum road frame on the cheap. My plan is to turn it into a commuter / beater, since I have some clunky parts to spare.
I've got a set of Shimano RX 100 downtube shifters from the early 90s that I intended to use. However, when I install 'em, the mounts seem to fit poorly-- the inside curve of the chrome shifter plate (the part that contacts the frame) seems intended for smaller gauge tubing. The Al downtube on my frame isn't especially oversized, but apparently it's enough to make the shifters not seat very well against it.
Am I out of luck? I really don't want to spend a lot of money to get this project rolling.