So there is no silicone between the sharp edge of the fiberglass tabs and the soft aluminum spar? Seems like there needs to be some type of a barrier to keep it from rubbing. Or, a small space to prevent contact?
I suppose you could increase the height of the RTV waves a little onto the lip. The picture in my manual doesn't show it going onto the lip very far if at all.

I would be careful not to get too close to the edge of the tank lip. If RTV squishes out past the edge when the tank is rotated and set in place it is going to make a good bond to the spar with the fabric impossible.