I just received and installed the new Kel Tec made quad rail on my Sub 2000. KT just started shipping these. Its a good quality unit but certainly not LMT or LaRue Tactical quality by any means but it should function well and do the job its intended. It took about 40 minutes to install and will make a nice solid platform for a vertical grip, light and a co-witnessable red dot sight setup. I like the way it looks over the OEM plastic forend also.
Here are a few quick and dirty photos
The Sightmark reflex red dot lines up perfectly for co-witness with the "iron" sights dead center in the lense of the optic and lined up perfectly with the retical of the reflex sight.