From what you say, you are not using the fiberglass drywall tape correctly. you first wrap the tape on to get a close fit for the seat. once you have all the tape arbors you need, first unwrap the first tape arbor that the seat will cover down to 2 or three wraps (so the tape will continue to grip blank. Now smear some rod bond on the tape and start wrapping the tape back on. The epoxy will go down to touch the blank as well as ooze up thru the drywall tape. continue wrapping until that tape arbor is finished or you run out of epoxy oozing up in which case you add some more and continue wrapping. I cut the end of the tape at a 45 degree angle with the short side nearest the seat. Now twisting the seat in the direction the tape is wrapped slowly push on the seat until you get about 1/2" (you judge) from the next arbor and unwind it and repeat the process until you are up against the grip. You now have a continuous epoxy path from blank to seat for a secure bond and a path for vibrations to go up from blank to seat. I would also recomend you get some teflon plumbers tape to wrap on ends of the seat and grips to help with cleanup.