y would they glue to covering?? thats the only surface otheher than steel that epoxy wont stick to... ne way, lets combine ideas. cut away the old fillit since its probably poor epoxy. then remoce about 1/4 inch covering on both sides of fin (1/4 on the fin itself as well) and epoxy some triangle stock in, sand the LE and TE of the triangle stock to make a nice transition then put a little piece of covering over. this whould fix the probem for sure.

remove covering where red is. the green is the triangle stock.