I've been playing with the SL15 and would like to recommend lifting the overall height of the fire control group around 2mm to better accommodate, 'fancy' drop in triggers. Both the fcg pin holes and the base height of the pocket. Some mechanisms like to use pressure from the bolt carrier to assist the user with their reaction time. The most fancy one in current litigation also requires a slight modification of the reinforcement rib on the inside left of the rear takedown pin pocket as well. I haven't played with many of these fancy triggers but assume many would benefit from the adjustment. You might want to R&D on that a bit 😉
