My new plastic fuel cell sags badly so i drilled a hole through each mounting strap and i'm trying to get something to bond a couple bolts to the plastic so i can draw it up to the straps but nothing sticks to the plastic, i've roughed the surface and cleaned with alcohol but no good. So far i've tried 2 part epoxy, super glue, loctite stick n seal and of course construction adhesive. Any ideas? Thanks.