Hello,
Here is an idea for making a cheap and easy velocity stack from a plastic air cleaner/choke housing. I cut out the center of a Toro 1bbl housing with my jig saw and cleaned it up with a disk sander. I results in a nice 13/32" strieght stack that also helps insolate the carb. The carb screws run into the cylinder on this one. It is necessary to trim the inner edge of carb side at about 45 degrees to clear the choke if used.

Dave