Lucked out and got a warm day of 5*C so pulled the trigger on installing the cable gland and solar.
I used VHB 1ā tape in a perimeter shape and Vās, then used 1/4ā VHB on the gland. After that I put a bead of clear RTV around everything in the hopes that will add some additional adhesion.
Next to tackle the remaining wiring inside, but at least got the solar hooked up to charge the battery 