well in my experience, not that Im an expert or anything FG Resin is cheaper, a quart is $10.00 a gallon $35 and it has the advantage you can find any at a dozen places locally almost wherever you are (@ least in north america) it does have the drawback of being highly toxic. though another option in the overall scheme is SmoothCast polyureathane plastic resins while thier inital cost outlays seem extravagant. a 1 gallon kit is $80 dollars 1 gallon is actually 2 gallons 1 gallon of part A and 1 gallon of part B. you can use really small batches to do the outside then slushcast w/ it on the inside, by passing ungawdly things like fiberglass and its non toxic, yes you have to order it online, unless you are fortunate enough to live in one of the few cities reynolds advanced materials happen to be located. just giving you a little more information. another thing to keep in mind doing armor isnt cheap you'll still end up spending several hundred by the time your done almost anyway you do it, the pep way.