SSS has a bad reputation for customer service, I ordered a ground recoil lug from them and refused to give a CC# until it was ready to ship. I have read good things about the Dark Eagle customs mag, probably worth the wait.
I had an FCP-K and it shot great but has the bolt release on the bottom which rules out any DBM kits, your only option is an XLR chassis, Kyle makes one for the bottom bolt release rifles.