Spiff, the best source for your inlet tube is the piece of Mac's header that you cut off from your new pipe.........well thats the only inlet tube that I was able to find.

JMulder, most of your LHS's carry the K&S tubing. I buy a 36" piece of the 1/4" tubing for a $2.00. Can make many-a-stinger with that $2.00 piece. And I dont think it matters that much how long he stinger is. I usually try to make mine as long as I need for the plane it goes on. For a PBF I make them shortand turn them down and run it through the coroplast. Then I flare the end a little , just enough to keep a tie-wrap from coming off. Keeps the top of your PBF really clean. As for fun fly planes I usually point them out a little straighter to keep them from getting bent.