another thing. I wouldn't use a drill press unless you're sure you can get the stinger adsolutly straight up and down.
the benefit of using a hand-held drill is the drill bit will naturally want to find the middle of the hole. If you happen to chuck it up in a drill press at a slight angle your hole may track off course and you could end up with a week spot. The pipe is aluminium so it doesn't take much to get it off course.
I don't remember what the final drill bit size should be, you'll have to source that on the website, but don't go any larger than that. You should step your way up to the final size, go slow with the drill and take your time.
Cutting off the flange changes the shape of the divergent cone which in turn changes how and where the pipe makes power. You don't need to leave much of the flange, just a small amount, 2mm at most. One thing I noticed when I made the change was I no longer heard the tranmission changing gears, the switch became seamless. Only if you slowly accelerated would you hear the change in gears.
You'll need to retune the engine for performance. With a 2 stroke, any engine mods that actually result in a change require a retune. If you make a change and don't require a retune, you probably did nothing. that being said, not all changes are good so get a baseline down for how your engine performs before the mod, then observe how it performs after the mod.
