Transmission works fine when fluid is full, but can't find the leak!

What is your question?

We have had the pans, gaskets, and pan bolts replaced on both pans. That didn't fix the leak. The only help was a repair shop in CA when the guy said he thought it was the servo seal while he was filling it. But that requires dropping the tranny... Is there anything else I can check first before fishing around with the tranny being dropped? It's a big enough leak that it needs to be refilled about every 300 miles or so.