Just drilled pilot holes in my Encounter. Nothing in there. I ordered a 21.5mm hole saw, which is about .08mm larger than the OD of the flange. Testing Marine Epoxy on one flange and a piece of 5/8" reinforced vinyl tubing. Had to order some G-Flex. I've got like 4 types of epoxy and no G-Flex. Might try some JB Weld too.