I just wanted to throw this out there as food for thought. I've owned 3 DCT e9x m3's now and began experiencing some occasional clunky shifting on my 2nd car. I had a visible leak around my lower pan and replaced the lower pan with a new lower pan and a viton seal($$). The shop doing the work also replaced the filter/filters and put in fresh OE DCT fluid. After all that the clunking was totally gone so I went ahead and loaded the full-GTS DCT tune (using instructions
here and version information found
here if anyone is interested). Granted I was only running on re-71r's and Cup 2's at the time but I never had another DCT issue on or off track with that car and that was even with the stock DCT cooler.
My current car has the do88 cooler, OE pan (not leaking last I checked), and even original filters and fluid, with the original fluid just topped off, same GTS DCT tune, and it's been flawless as well, both on and off track.
My theory is simply that the leaking is more the issue and when folks are experiencing clunkiness or overheating, perhaps they are just low on fluid?
Keep in mind that our DCT fluid can leak from many locations:
LINK.
and also that the DCT refill procedure is fairly complex:
LINK and
LINK.
There are surely some other benefits for the replacement lower pans such as the increased fluid volume, less leakage prone (or no leakage at all), shedding heat more quickly, baffling, etc., but my general thinking is that for folks on 100tw or higher tires (what I have experience with) the solution may simply be to fix your leaks as they arise and top off the fluid if you've had a leak.
I do get the idea of trying to proactively prevent future leaks also and all that said I'd probably try for my OE-pan + viton seal fix or go for a SLON pan if I had another leaking lower pan. If I had a side or top leak, well that just sucks when that happens
