I think the seal on the hardtop is all one piece, and it is held in by brackets and friction. My hard top leaked a bit at the same point. I cleaned both surfaces really well, and then applied some 3M silicone lubricant. This stuff works great to refresh your seals, but don't get any on paint or glass as it is hard to get off. There are little drains in there and they can get clogged, so keeping it clean is important. I put the description of work on how to repair this common problem for the 129 chassis here. I hope it helps! Happy Benzing!
Brian
http://www.mbca.org/northtexas/129_technical.htm