Yea, ive got a good air rifle sight on my P90, plus a green laser sight, B&T tracer/silencer, Safariland Torch, and a Safariland Single point harness I custom installed in the rear
MP40 sounds sweet, perhaps bring both just incase it is abit too hot. I never bother with a sight at the mall, just a dirt-cheap pistol torch on my p90 lol.