Rotocasting is the PROCESS that is used to distribute the vinyl material in the mold while it is still in it's liquid state. Think of a gyroscope or gimble with the mold locked in, rotating in 3 different axis. This is so the material distributes evenly throughout the mold. The Don Post & Rubies helmets are made this way & are flexible & durable. You won't have any problem holding the equipment you require but watch out for what type of adhesive you use to secure them. Velcro works great for batteries & good old hot melt glue is excellent for anything else. Don't use the kind available in the craft section, not all hotmelt glues are the same, use a commercial grade. I found some at Home depot (Arrow Brand Bss6-4) & I haven't been able to find anything of equal or better. Hotmelt also has the advantage of letting you remove parts without damaging the helmet. Simply break the glue bond by putting a few drops of methyl hydrate on the hotmelt. It will wick under the hotmelt & you will be able to peel the part out. The methyl hydrate quickly evaporates & will not damage the vinyl helmet or harm painted surfaces.