I'll be joining the Silicon Removal Club when I begin work on my 65 Shasta. It is sealed tighter than a drum around both sides of the J-rail, the windows, and every little screw hole. Holy Moly! I haven't looked to see how they sealed the roof vent, I'm scared. But I can attest to the fact that it does not leak at the moment. A lot of the silicon around the J-rail is thick enough that it just pulls off clean from the paint, thank goodness. I think the challenge will be removing it from the rail.