I own the clasp (in Ti for my 45.5 PO), a 2220.80, 2232.30. I can 100% guarantee that the clasp will not work with the end links on the 1503 bracelet as they don't have threading to keep the screws in place.
Even with the appropriate end links, it will be a very poor fit. I've tested this at my local OB. If you have a 2531.80 or similar, the easiest option if you want an adjustable clasp is to buy the new screw and pin bracelet ($760 or so) and the 1154 clasp ($117). The bracelet is a direct fit, and is much more robust and won't stretch like the 1503 does.
Edit: here's a thread from WUS:
http://forums.watchuseek.com/f20/wh...asp-117stz001154-3609002.html#/topics/3609002Click to expand...