Hi folks, some time ago a caster told me of a process he uses to
enlarge an item by casting. I don’t know the exact process, but
he put the rubber molding over (no contact!) a vessel with
gasoline under cover in order to soften the vulcanized rubber,
and it will “give” under the pressure of injected wax. Time of
exposure will have effect on how much larger the wax will be, I
think. Perhaps worth to experiment a little (with molds of
little worth of course). good luck, Markus