I have a DPMS Sportical its a 16 " barreled carbine which I purchased in 2008.Im wanting to get suggestions for the best route to follow.My gun has a Vortex strikefire red dot,a harris bipod and thats about it.I was wanting to get rid of the bipod and put a vertical grip /bipod in its place.I also want to change the stock to a collapsable that has alittle more cheek rest,maybe a Vltor.My gun has the round stock forearm on it now.Is there a way to attach a section of rail underneath the fore arm or how do I got about attaching these accessories.Do I have to go the drop in railled route.