The seat storage box appears to be plain old ABS, not a the best candidate for epoxy to the bottom of the seat pan. I am planning to simply rivet using wide rivets & washers. The only wrinkle is that the seat stiffeners run on the sides of the seat underneath and interfere with the flanges on the box, requiring that they be trimmed to almost nothing in places. A friend is recommending the top-mount option for the flange, which would mostly eliminate the problem with the stiffeners.

Any suggestions or photos of other installations ?