Would you mind posting what your temps are when you get this setup going? I see these alternate location installs often enough to make me curious as to how well they work. I want to impress upon you that I am in no way picking on you or being negative in any way, shape or form. I like the work that you are doing and would like to know how well this works. If for nothing other than information.
My understanding has always been that any heat exchanger of this style has to have airflow through the fins and cores. Your install has air more or less going across the coolers. I've seen this more than a couple times on various street rods and whatnot and am really interested to see what the temps actually are. It's one thing to have someone say they've never had a trans problem, but to have someone show what the results are would be cool.