Check my posts from a few pages ago if you're interested in which skid tray I installed in my GTI. I don't remember what I bought and I don't have the receipts anymore but my mechanic didn't complain when I asked him to install them for me so I'm sure they all fit with little to no issues. The increase in fuel economy is nice and as I said before, it would have done wonders in lowering the CAFE average for VW in USA.
As for track performance, I get overheating issues in a 20 minute lapping session at CTMP DDT on a hot 30C day, but that's to be expected as the cooling is weak in our cars. I generally can only do 1 hot lap at my 100%, and then have to dial it back to about 80% to let temperatures come down a bit or hold steady while I still have fun driving fast. I had the same issues with the OEM short skid trays so I doubt it's the reason why I'm overheating.