Glad I sent a bunch of my 2.5's to Provape last year to get them converted to P3. IIRC it was under $20 each and Provape ate the return shipping.Just got done chatting with Zen.....if you have a slant top that you want converted to P3 you better hurry. He doesn't have many parts left.
Zen is a bit more pricy, but I highly recommend the P3 top over the tapered top and he is currently the only real game in town...