Leaking issues in my 200 4R - any gurus available?

The vent on a 200R4 is on top and points toward the passenger side of the transmission ... right about the front right of the pan. It fits so tightly in the tunnel I can't see anything up high. I suspect it's coming out the vent and is heat related. I drove it one cool morning and not a drop leaked. I blew out the cooler to be sure it was clear. That same evening it was smoking and leaking. Didn't stop me from racing and embarrassing a Corvette, however.

I spoke to Art Carr, who built the tranny. He says 100% it is getting too hot and pushing fluid out the vent. He asked if I was running a cooler, which I am. He asked what style, and it is a cheap tube and fin style. He said to get rid of it and install a stacked plate style cooler. He says they are the best and most efficient coolers available. I asked him why it was fine for three years and he said I was probably riding right on the edge and age has made everything less efficient and now I'm over that edge. I bought a B&M Supercooler stacked plate cooler. It gets installed tomorrow night, so we will see.