Having a go at making a head mould so I can covert some fins. The pic shows what I have done so far. I am using my most in-spec fin as a plug. Can anyone see any problems with it? Given that Powerbox has so much taper I dont think there will be too much trouble withdrawing the fin as long as it is well waxed. Or am I standing into danger? Opinions please!

(Please excuse the crude nature of this prototype)