We used 3M WindowWeld for the front lexan and it did great in the rain (and snow) at Barber and ECR, but we pulled our Lexan windshield, installed the WindowWeld, then put the Lexan back in and laid a small bead over the top too.
But, we were able to remove and re-install the "glass" itself to create that seal. And it did work great. You could probably use it in the same fashion over the top of existing seals, but I don't know if it would adhere very well. It is some thick, sticky stuff though.
You can get it in a caulking gun type container at AutoZone. Caveat: look at the expiration dates, you want the stuff that is the newest (i.e. has the date furthest in the future). This stuff hardens up quickly in the tube, and it's not easy to get out even when it's fresh. The old stuff is practically impossible to squeeze out and then it sets up fast and doesn't last very long. Learned that lesson the hard way.
Alternatively, you could use some silicone door/window caulk from Home Depot over the top, that's cheap and easy, but I'm not sure how well it would last at speed, since residential door/windows don't tend to achieve the same velocity as even the crappiest Lemon. Cheers.
Pat Mulry, TARP Racing #67
Mandatory disclaimer: all opinions expressed are mine alone & not those of 24HOL, its mgmt, sponsors, etc.