Sealing Headlining Edges

One of the things that has been delaying gluing the headlining in (other than lack of time) is because of a warning I got from the guy I will probably use to install the front and rear windscreens. When I incidently mentioned that we had made our own velour headlining he indicated that suspended (or bow) headlinings were usually vinyl for a reason. The reason is that where the headlinings wraps around the body seams on the upper edge of the windscreen openings you can easily get water ingress. Thats means if the headlining can soak up water (capilliary action or "wicking") then it will gradually stain inside the car - starting at the edges. In our case the headlining also runs down the inside of the rear pillars so it's a concern.

So I have been looking for a sealing product that would stop this from happening.
I found this on a dog whelping site - I have no idea why they sell it. It's also sold by lots of camping places (not in Australia though) to help seal tent seams. The whelping place was in Australia and shipping was free.

The idea is that, once the headling is glued, I run along the exterior exposed part of the fabric and carefully seal it with this.

My concern, other than it not working at all, is that it may harm the rubber seals so as soon as I get it I'll apply a little bit to a spare piece of the 1/4 light rear window rubber so at least we will get some warning if it's a quick reaction. Some sellers recommend it for rubber shoes so it should be OK.

That's unless someone out there has a better idea.