The gaskets are not going to keep 100% of the water out, that is why there are four drains. Keep them clean and if you park on level ground you should be good. If you don't, the magnetic vinyl works great as i am using it on a 100 series right now.
On my 80 if it is out side i park on a pretty good incline and it is fine but my drains are clear. If i have an issue i will use magnetic vinyl as i like using my sunroof on nice days.
100% correct. The seal around the glass is a dust seal, not a water seal. At best it will only slow the intrusion of water. While the sunroof seal was not intended to be removed, it was glued on before the assembly was put together, so in theory, if you had a rubber seal with the same, or similar enough, cross section, you could replace it. I'm still hunting for one. Toyota learned their lesson on the 80 series and designed the 100 series with a replaceable seal, for about %40 or so. Way better than replacing the glass, but that doesn't help us.
The best you can do is to coat the rubber with a good rubber protectant and hope for the best. Having said that, the protectants on the market will only work to slow the degradation, they will not repair degraded rubber. So if they haven't been used form early on in the life of the seal, they are band-aids at best.
The only permanent solution is to do what Toyota did on the 120 series/LX 470/460: run the drain lines from the sunroof through the floor. If you do this, and there are two ways in can be done, your sunroof will not leak into the cab.
Method 1: pull the drain line out of the pocket behind the kick panel and run it though the drain hole in the floorboard. Not my preferred method, but it will work.
Method 2: replace the front drain lines with new (or used) rear lines (which are longer, but the same diameter). remove one of the two body bolts holding the rear lower fender edge onto the body (you don't need both of them) and enlarge the hole to accept the new drain line, or drill a new hole large enough to accept the new drain line. Problem solved. Permanently. FWIW, the rear drain lines are just long enough to exit the body and discharge about 1/2" below the running boards, so there's no chance the water will foul up anything else.
