Just to finnish up your question about my alignment of the exhaust tube. I pretty much eye balled it. Since I drew a center line down the board, before I tack welded the exhaust tube on, I mounted the front end assembly. I also fit the exhaust tube so there was a 1-2 mm overlap onto the front end assembly. The wire exhaust bracket was carefully mounted to provide the correct alignments also. All I did was put the engine together, and place a tack weld. Since I took my time in making everything straight, and true, it came out that way.
As for your starting system, I think you are getting a little carried away. Your engine was not hard to start at all. It was downright easy, and most of the stuff I used was right off the shelf (including my 30 gal air compressor HEHE).
What you should do, in my opinion, is put together a cheap, standardized list/ instruction for how to create the ideal regulator, sparker, and starting air. I can help you with this as I was in the same boat a few weeks ago, but I had no problem.
With these suggestions, everyone can just GET **WHAT THEY NEED** to have a successful engine.