Pretty cool,
I would make a suggestion. 1 the fuse and 2pin plug- my rec would be a simple pvc juction box.
Similiar to this-any hardware store, they can be had blank or threaded knockouts. Hole drilled in bottom to match solar plug location in roof, maybe offset to ensure enough cable. (& future ant coax?). I mounted with mounting screws inside of the box instead of exposed 'ears'. Side knockout with gland (could just caulk out). Just see both subject to corrosion laying there, also though you said 'cap' would offer protection, plus cap removable to access without disturbing any sealant etc? but you may have on the round toit
Second is the size of fuse-where did 10amp come from? Nominal on sunny day you potentially (hopefully) could surpass 10 amp, but fusing should be based on the short circuit rating of panels (5.75 amps x1.2=6.9a, twice=13.8amps?) While for protection smaller could be considered better but as this on the roof...