If the mask you bought seems to have wider slots / fewer edges than the optimum for your telescope, you can try stringing it like a tennis racket, with one (or more) pieces of opaque string / thread running down the centre of each slot. You can either drill holes and string it like a tennis racquet, or you can glue lengths of string to the mask with a hot glue gun or similar. Make sure to keep the strings taught and parallel to the edges of the slots.
Voila! Twice as many edges, with very little loss of Aperture.
In fact, you can make a very effective Bahtinov mask using ONLY string for the diffraction edges:
http://njstargazer.org/Bahtinov.asp
