That stuff is usually used for making transparent paperweights etc. If you are in england, try Davids fastglass. They sell it in places like Halfords and Taskers. Infact, most car repair/supply places have it.
Well, all you will be wasting really, is a bit of paper. Your first pep piece will probably be quite bad anyway, that is, until you get your pep groove on. The good thing is, it's all experience at the end of the day.
i use davids fastglass and i get it from halfords its your best bet mate and btw the kit is a good option but the mat is hard to work with but it sets your peice rock hard i did another helmet with it today