I am currently building 2 bikes and have 2 miche supertype seatposts. I just picked up a velo saddle on saturday and I CAN NOT get it to fit either of my seatposts. The supertype has a (ridiculous) rail clamping system where the front has to hook into a groove, then the rear swings down to clamp onto the rails. For some reason, once I get the front hooked into the groove, it wont clamshell down onto the rails. It seems as if the rails are too large or something. I thought saddle rails are supposed to be universally the same OD? Has anyone else ever heard of this problem?

it might have something to do with the distance between rails on your saddle(s) and the distance between rails that your seatpost was designed to accommodate

I had the same problem, the saddle rails and the seatpost grooves didn't look like they lined up correctly. But when you tighten the seatpost's bolt tighter and tighter they fit together perfectly. It took me a couple of tries to get it right.

simply just use a zip tie and squeez the rails together.