I just spent this weekend installing a brand new Bestop soft top on my TJ. It was a nightmare. I was in an area with no internet available so I had to wing it on my own. I followed the instructions to the letter but there was no way that I could get the top to fit. The header was about two inches away from fitting and I couldn't close the catches at the top of the windshield. The instructions say that the temperature should be above 72 degrees and it was just about that temperature when I attempted my install. Unfortunately, I was next to the ocean which meant the cool breeze prevented the top from getting the benefit of the sun's rays.
Earlier today, I was able to get internet coverage and I found a previous post on the forum about this problem.
It was suggested to disconnect the rear of the top and push it all forward. Once you do this, there should be no problem installing the front clasps.
I followed this advice and it worked. However, now I was unable to stretch the new top to fit at the rear. The solution was to install all the windows and seal it up as good as possible. I ran the engine at idle for about a half hour with the heat on full blast. The heat was enough to stretch the fabric and I was able to make the connections at the rear, with the assistance of my wife.
I drove it for about two hours this evening and no problems. I'm going to leave it all sealed up for a few days to ensure a proper fit before I even think about taking the top down.
Thanks to the previous poster who gave the advice on solving this common problem.
I hope this solution works for you too.