Oh great on that battery cover! I was about to make one from an old wet suit leg. After finding water in mine from a muddy ride I've been taping mine up. Seems like a really bad design on the battery/frame interface. Does Giant not know of any automobile engineers who've solved this problem a million times before in cars that drive all winter through salt spray? It is also a good idea to make a rear fender stub that goes from the bottom pivot up to the top linkage. That prevents splatter of the frame bearings and motor from the rear wheel.
This cover is good as well and was recommended by other riders: Fahrer E-Bike Battery Akku Cover Tube Blue, Bikeinn