It should be said that you can't affix a rail to the underside of C9 without modifying the frame and covering or damaging the serial number plate. You will have to glue or screw the rail on to attach it.There is a 3D printed black high impact item from JS Arms https://jsarmsco.com/c9-poly-framed-lower-picatinny-rail-for-laser-or-light/
I should've also said "I think it looks like crap"It should be said....