Not sure if the tri forum would be a better place to ask this...I recently bought a pair of Syntace C2 clip-on aerobars, and they are designed to fit 25.4 mm bars and slightly larger. I thought my bars would be OK, but they are 25.4 in the middle, and more like 23.5 out where the clipons would attach.
There are actually two road bikes I'd like to use these on, my old Coppi here in Wisconsin, and the '84 Ciocc that I have out in California, where I'm doing a full-distance tri this summer. I had my nephew measure the Ciocc's bars, and they seem to be similar in size to the ones on my Coppi.
I tried wrapping some foam adhesive tape around the bars, but they still wiggle a bit. What should I try next? I'm thinking of cutting up a tin or aluminum can to make a shim, and put that over one layer of black friction tape.