Spent some considerable time roof testing during last night's downpour, and the findings on the O5S material is that not only does it look good but it was pretty well waterproof, beading nicely on the outside while remaining touch dry on the inside. All the zips and their stitching remained perfectly dry. Yes there were a few water beads on the lower corner seams coming though a few stitching holes I had noticed before the rain test, but not enough to write home about, or should I say to write to VW about. I intend to get our VW Dealer to spay it with Aquatex, which he said he had done for another customer. Hopefully this will absolve us of any future warranty problems.
BUT, water penetrated in from under the lower edge of the rubber seal between the fabric and the bodywork. Pooling in the front corners, also coming in from around the hinges then running down to under the front headlining.
What I think was happening was that water was gathering in the channels around the roof rubber seal because the drain holes couldn't cope with the quantity of water, then leaking UNDER the rubber seal that is being pulled upwards because the fabric is very taut in the corners.
VW are aware of this type of problem because it affected their EOS previously.
What's the cure?
1.Not put the roof up during heavy rain, no.
2. Aquatex the outer corners, yes.
3. Mastic under or around the rubber seal?
4. Reduce the tension on the bellows to stop the seal lifting?
5. Fit a better rubber seal to the bellows. Can't see that happening at this late stage.
6. Kick it around hoping it will go away, probably.
Over to you VW!