Cannot assist with the ''Seams'' But i had the same problem with my old Avan poptop, with the rope track leaking down the body, I used Clear Roof and Gutter sealant, just a thin bead along the length of the rope track, solved the problem for the 6 years i had the van,

Who told you Not to use Silicone ??? And for what reason ?? 

Silicones aren't silicones. Some silicone may not be suitable while others are. Go to a reputable seller and ask for advice or use Mr Google and phone the company that make it. They will share their advice freely and willingly.

in relation to the seams leaking. If it is canvas, they may need to be water treated. When the needle goes in to thread the thread, they cause a hole that will be bigger than the thread left behind. Wet it until it is soaked. The canvas when it dries will shrink slightly and close the hole up. We had a canvas Camper Trailer, water treated it a few times before it was used and before it was needed and it never ever in the 6 years we had it leaked from a seam. Vinyl may need a seam sealer, speak to a canvas or tent maker in your town. They should be able to help.

I am finding that just mentioning that you are a GN illicits a good response and help is given with a smile. Might not work forever but it is at the moment.

Bob

A candle? Now who woulda thunk? Thanks for the tip, Brian. A couple of spare candles in the tool box sounds like a good idea.