The mold is for a seat. Haven't started yet. How much wax if I am only going to use the mold once or twice?

I built a fiberglass soapbox racer for my daughter a few years ago and am considering doing another one or maybe two. I'll use the body I have now to make the mold but I want to do it on the cheap, so any way to save money will be considered. (Not much call for professional soapbox racers!)

Ian