What sticks to Coroplast??

I've got an enclosed bottom on my TT which is basically just large Coroplast sheets screwed to the flange of the outer frame. There are a few access points where the pigtail goes in, the fresh water drain comes out, etc. that are nothing more than flaps taped shut. The problem I am having is that nothing seems to stick to the Coroplast long term. I've tries duct tape, all-weather duct tape, Gorilla tape, reinforced duct tape, all work for a while and eventually just let go leaving the access panel flapping in the wind.

I even went online and bought special underbelly tape specifically made for mobile homes and the same thing. I clean the area with alcohol pretty thoroughly and it seems like I get good adhesion every time but a few months later it lets go.

Anybody have any suggestions or know of anything that works????