I'll amend my comment to say that an 11x14 paper for an 8x10 contact is starting to get into the realm of wasting paper though. 5x7 on 8x10 is very normal - you've got a 1.5" margin all around, which is a nice amount of breathing space, but not so much that you'd be able to use those unprinted margins for something like test strips or even other prints. Not true with an 8x10 on 11x14 paper - give the 8x10 inch print a 1" margin, and then you're still trimming off enough paper to make one and a third 5x7 prints.