I have one more idea for increasing the PAR from this. One thing the "cans" do is concentrate the light into a relative small circle. The longer the "can" the smaller the circle. So, tomorrow I plan to add a 3 inch long extension to the "can", made from aluminum foil, and measure the PAR with and without it. That should tell me what length of "can" is needed to get the PAR I want. If it is a reasonable length I can make new "cans" from cheaper material than the thick wall aluminum pipe - PVC, thin wall aluminum pipe, even cardboard, using aluminum foil for the reflective surface for the non-aluminum materials.