time to add my thoughts...
one, brazing doesnt really work on tuned pipes unless you take the time to use lap joints. past experience
TIG is best, followed by oxyacetylene. (welding, of course.) migs tend to make nasty big lumps unless you have a GOOD mig welder (unlikely...) stick.... possible, if you can do it and can track down 1/16 rods. butt welding thin section tubes, its far better to tack every 91 degrees until the whole joint is welded rather than try to lay long beads. makes it hard with anything but TIG.
i did try brazing a pipe and intended to use aerosol cans, but got lazy and just used 1mm sheet, butt...erm...brazed. it failed within ten minutes
then when i went back over it with reinforcing straps, it just cracked next to the straps... was fun, but not the best approach.
two, shoving the stinger up into the reversion cone only has one effect...it reduces the volume! but make sure the stinger ends up almost in the belly, it has detrimental effects if its only halfway up the reversion cone for some unknown reason.
if you take the time to find any of my threads on making pipes, youll see i used to gut a HT silencer, and trim the end so it would fit neatly onto the reversion cone. worked really well.
3, the difference in making a "guesstimated" pipe and using some software/pipe calculator based on the actual port timings makes a huge difference! and then its best to use a program such as "cone" to make up all the little pieces. more joins the better! it allows for nice smooth bends. i found that abrupt, angular bends (ie, notch and weld type bends) does not work for making effective pipes.
my method was to design a pipe. divide each section into easily managed sections (often by fudging numbers so that lengths divided by diameters resulted in nice round figures ie, 16 pieces of 20mm long, with 1mm increase in diameter per length), get some wire, mark off each section, figured out the angle required between each section, which sections could be "joint together"(why weld three straight sections together when they can be printed out as one?), etc. then printed out each sections template with "cone". bend/roll everything, tack it all up, finally weld it up, voila!
