i would just make a rubber mold and a mother mold from the pep helmet after you bondo and sand, that way you have a pres-teen master and then you can use your mold to slosh your resin inside.. I also do alot of vacu forming and honestly you do not want to have to split your master just to do some pulls, because after the pulls you will have to trim and rejoin the halves back togeather therefore creating a join line down the middle and more finish work. the only thing that I would use a vacu former for would be back and chest and cod and buttplate pieces or weapons. just a little information for ya to think about