Duetto, Flair, etc high top window leaks

Anyone else have leaking high top windows? The offside one leaked from the join at the top centre of the frame ever since I bought the van around 6 years ago. I had hopes that Craptain Crolley's Creeping Crack Cure would fix it, as it's pretty good usually. But sadly the leak would always return whenever I took it somewhere mountainous. I've come to the conclusion that chassis flex and the big rollover bar halfway along the roof (which from a safety point of view I'm glad it has) causes the roof to flex, and CCCCC simply cracks up under the strain.

So... earlier in the year I removed the window blind and shelf below it, the over-cab locker front, both front roof liner panels and the offside side liner panel in order to get the window out - and it was a pain of a job to do. I order a new mastic sealant strip from AS, and it turned out to be about twice the thickness of sealant than originally used, plus they recommend a bead of silicone sealant around the outside now. All done, I would have only needed to remove one more panel to change the sealant on the other side, but why fix something not broken?

So I go off to Scotland, and as soon as I get there the nearside one starts leaking!

Which means that now almost all of those panels have had to come out again. The cause appears to be that one of the aluminium U-shaped clamps had slipped off the frame because it had been installed just a little too far away. Having drilled another fixing hole slightly closer, it seems to be in a better position now.

BTW, if anyone has this problem on one window and wants the remaining sealant strip, let me know. You can only get it from AS in (IIRC) 8m lengths, but each window only needs a little over 2m, so there should be enough left for one window (but unfortunately not two...).