When contacting 8x10 negatives, I would suggest going for the next size up (12x15). Then you can contact onto 11x4 paper if you wish, or eventually use it for alt processes (generally one wants a good amount of border for those.)

I just think in the long run, buying a larger frame will save you money -- you won't have to buy a larger frame in the future, and the larger frame in handy to use for 8x10.