Shoe Fit

One option to consider would be to add some insoles to them--either by removing the insoles they came with and replacing them, or simply adding to the top of the current ones--this will depend on how much extra room you have. Most people have different leg lengths as well, if your shorter foot happens to be on the shorter leg, only add an insole to that shoe. The other option would be to take a ride in the rain--I have found that my shoes always kind of "snug up" to your feet when it rains--this will probably take care of the one thats too big. I wouldn't worry too much about it if you have to tighten one shoe more than the other, as long as its not uncomfotable. Ride in them and see how it feels! Good luck.

Jeff

Don't forget that your feet will swell some after riding for a while. That may snug the shoe up for you. I also remember reading somewhere that it's the bottom straps on the shoe that generally cause numbness and other discomfort to the feet. So cinch the top strap as tight as you need to.

Mitch

The big problem I have is that I cannot ride in the shoes. The person I bought them from is more than willing to exchange them for a 42.5 as long as they are unused. I'm just concerned that with my right heel slipping out of the heel cup, I'm going to have some problems with hard climbs and sprints. If I go with the 42.5's then my left toe will be crammed against the toe box. Which is the lesser of two evil's???

As has been said, your feet will probably expand as you get hotter, and most of the pulling is done from the sole of your feet too. You could always get some heel grippers for normal shoes which will stop the slipping. Slightly larger must be better than slightly too small.