I have seen it both ways, and the two person version is much better. The costume/character changes are a lot of the fun on the show. If you can get please the board with a two person cast, please let the dressers have a bow (it will probably take two per actor), this always pleases the audience. I do not know if it will help, but the cast does not have to be two men, it could be two women or a man and a woman.

If you must add more people I would suggest as few as possible (maybe four people total instead of two), I think all characters fully cast would really take away from the show.