asymmetric bonzer adjustments

I recently made an asymmetric bonzer, and have had mixed results… I find it great on my heel side, but a bit stiff on toe side. It was designed for good waves, head and a half to two and a half, to be drivey on toe side and looser on my heels, so nearly there… I realise that it is probably a rocker issue ( or possibly concaves) so was thinking of a way to alter it.
My current idea, is to install some (lokbox) boxes behind the rear bonzer fins and try out different 6 fin options, and if all fails, still have the original fin set up. Opinions greatly appreciated.