Several questions first. Did you extend (open up) the splines on your T5? If you did, did you slide your clutch disc onto the main shaft to insure that it would pass back 3/16-1/4" past the end of the splines towards the transmission? Which disc are you using? Did you get the disc installed with the correct face towards the flywheel? Was the backside of the disc (towards the throwout) fairly flush with the disc surface?
If your transmission bolted up without the disc you've pretty much isolated the problem. You're not the first person to have this same problem so don't panic. The key is to get the splines massaged so that the disc slides back past the end. I ran into the same problem with mine using the RCF-4201 disc.....made the additional cuts and mine is on the road every day.
I've got some pics of the spline tweaking in my webshots shoebox.....someplace around pg 6-8. Hope this helps.
