Originally Posted by Bob Dopolina

My guess (remember this is a guess made without ever having seen the frame or actually believing that any problem exists) would be that you couldn't run a first position 13T cog. You'd have to run an 11T or a 12T (FYI the most popular selling Campagnolo cassette, by far, in these parts, in the 12-25 I mean who the hell runs a 13-26 on this frame? Why not just plunk on a triple and a rr rack and let's go for lunch!).