What kind of Round Tube Did you use inside the 1 1/2 sq tubing, and what are the deminisions of it, and where could I get one of them as well as the FCG box? Thanks in Advance...DocFurniture is from Sarco. Receiver uses 1 1/2" .120 wall square tubing with a round tube inserted inside. (see pics). Sights in the pics are Soumi.