I have on several occasions cut a flap open on the back of a Hayes tank to install a bronzed filter pickup as it would not fit thru the front hole, trying to keep down the fuel foaming on profiles. Scuffed up the plastic and used JB Weld to glue back, so far all have held for a couple years. Also if you are just poking a fuel or vent line thru the plastic i would think silicone would hold it in place and seal if it wasn't being moved around all the time. Maybe JB would work for that also.