I saw a P19 main a few years ago that had been modified to a square top by Glazer, I think. Looked great. As far as Dacron not working? Not true. I had one on my H21se for a while and It was fantastic. There are a few Dacron square tops running around here in Texas that are holding up very well. One is at least 10 years old on a 5.8 and made by Calvert (the same maker of my 21se main) and is still raced quite a bit. But back to the original question about modifying, I think that's the way more than a few P19MX's were done in the first place.