What Buzzcut said, contact Bigfoot....Call them no email.
From what I was told, the screws go through the Fiberglass and then into a block of wood/plate. You can confirm that by measuring how deep the actual hole is. The glass in the corners is very thick, maybe 1/8 to 1/4 in.. So if the hole is deeper than that you will know that there is a plate there.
So if they are not helpful then think about doing the following:
The best thing to do in that case is to drill new holes in the Jack bracket and then into the camper.
I would put the original screws back in the holes to hold the plate in place, just in case it is not glued to the inside... You do not want it to become displaced! Make sure you have enough holding strength to do this. If it feels that the plate is loose then you may need to do the following..
Fill the existing holes with West systems resin and filler, then drill them out to put the existing screws back in. Not much holding power but just for looking good.
My jack brackets are bedded in with silicon.
So when you have all your holes drilled I would remount the bracket without the bedding, then remove it if you are satisfied then use the silicon to bed-in and mount the bracket.
Jim
