500SL R129 Hardtop leak
 

Raising an old one again, but I have still not understood exactly what to do...

As fall falls, I will no doubt put the hardtop back on my 1990 R129 some time towards the end of the month. (No rush, as it was 26C/80F in Geneva today.) With the soft top, there is absolutely no leakage, even in thunder storms. With the hardtop, in heavy rain, I get a very small leak about 92/20cm. behind the A pillar on the right side window. The left is perfect.

None of the seals have ever been replaced in the car since new. I can't see where the leak could be. Where should I start? (I have seen the earlier post on fixing a leak at the seal on top of the A pillar, but I don't think that is where it is, though I will accept correction on this.)

Momo