asymetrical fin set up

Mate of mine this weekend lost a Fcs TR4 [51/2’‘, 5’']on backside of the board, which he was using with a 61/2 ‘’ centre fin on his 9ft fish.I suggested he put in his larger side biter as a replacement and ride it asymetrically . Anyone had any experience of this or am I completely insane .

Cheers

mpcutback