Margin when using multiple brokers

[blueberrycake]

I was wondering if anyone has any experience with using multiple brokers for your trading. In particular, I'd like to use one broker for electronically traded futures, another for pit traded contracts and yet a third for my stock transactions.

While the basic logistics are manageable, the problem that I foresee is one of margin. Namely, if I want to put on some large positions in one set of markets, I can end up with insufficient cash in the account for margin because most of the money is actually in the other accounts. Is there any way around this problem?

-bbc