im not tring to put you down or anything but your foreman proubly wouldnt do too great even in the 500 class. since this would just be for every once and a while then sure you could race it, you proubly wont do too good but you could race just for the experience. you said your friends race in GNCC so im gessing you have been to races, but if you never been to one i recomend going to one and see what all it is first. GNCC is pretty hard on a rider. racing is in my blood, i love any type of racing. i would love to race in GNCC since i do have a bike that is up to par but i know a couple of people that race and they said that it is not common to trash your plastic and wheels just racing normal. that is what is holding me back from racing in GNCC. if this is what you want to do though, go race and have fun.
-Aaron