Did a lot of thinking fer the front side gap covers and this is what I came up with. It's a door based gap cover that should flex enough with the trailer rolling. The sliding cover is to allow the trailer lid opening/closing without crushing the gap cover. Obviously, I still have to trim the covers down once I git the trailer hooked back up and determine the best size fer those covers. I might end up moving the triangle covers to the inside.
Closed...
Open...
Front view...
Even had some time to install the aluminum flashing so the clear gap cover doesn't wear into the Tyvek/Coroplast lid.