I ran the 46 with the crimped down tubes yesterday, and found that it helped tremendously. It was fine from start to finish with no landings to re-adjust the mixture. Now I can work on reducing the pipe size with tubing.

It's too bad that more time is not put into designing such pipes to get at least a reasonable facsimile of useful pressures and back-pressures beyond tacking a bit of tubing and machined aluminum together. There is certainly a lot more science and experimentation involved in making a 2 stroke run properly and efficiently than has been expended in producing the Bisson Pitts muffler. The Slimline Pitts muffler would probably be even worse due to lack of an expansion chamber.

Oh well... Sometimes you just have to make or modify things yourself to get them right. It's all part of the enjoyment of the hobby.