Crossplaying, as it is defined - is the taking of IC knowledge from one character and OOCly transferring that knowledge to another of your characters for IC use. IE: Using OOC knowledge for IC purposes --big no no-- However... You -can- have two characters that have the same knowledge about a certain situation, if there were IC means of doing so. That is not crossplaying. If one character has an arguement with someone, and that someone tells another someone that they just had an argument with player X and rumors keep going until another of your characters ICly hears about the situation, then that is -not- crossplaying. Your character legitimately found out information that was passed through a chain of events.
I know for a fact it's a hard thing to keep balanced as well, having several alts on different games that are either related to each other in some way or know each other for various purposes, often times enemies of each other so that they do not have to interact often, or not at all.
Anyway, I think that's all I wanted to say, since I have had experience with this sort of stuff elseM, trying to keep everything situated and organized so the right people know the right organized so the right people know the right information, and making sure that those who should not know things, do not, all in an IC fashion.