Simple cuts ... An example of some cuts ... note this is the plate portion of the mount only.
You will note on the Epson 500 projector the actual name of the projector is cnc laser cut right into the plate. Note every time the cnc laser cutter is cutting it does cost money. Try doing this by hand? Note the cuts for the BenQ 8700 mount and for the Z3 model that conform to the exact dimensions of the case and venting.
I use steel because the gauge of steel used works the best. I discount using plexi glass or other materials where heat will eventually degrade and revise the molecular structure of the product and invite the possibilty of failure.... ie getting brittle over time cracking and possibly falling on someones nugen.
I don't make a generic product because I simply don't believe that it would function ergonomically to the piece. This leaves a quandary of sorts to have inventory of some units that do not become as popular as anticipated.
Some pieces I refuse to make because of the case design from the manufacturer is too weak to rely on.