Sure, Vasek, glad "the barber is still in"! I always try to post my final learnings to return the favor and hope it helps someone later.
The original forum was here:
http://www.rcuniverse.com/forum/m_44..._2/key_/tm.htm
Post #23 by flyer95 was the clincher for me. He had a 9mm bore carb working great on a SuperTigre S3000! I generally do NOT get into machining (whittling?) my own engine parts. I know how but no longer have lathe access.
And the Idle now sounds like this:
http://www.youtube.com/watch?v=M48Q8EBw7ks
But I attribute the nice idle to the break-in and final low needle adjustment. The sleeve mostly enhances fuel draw.
No pics of the mod, but installed, at WOT throttle position, you would just see a 1mm brass ring in the ID of the carb barrel. The 12mm carb bore hole thru the larger diameter rotating part of the carb leaves a saddle shaped surface at the OD top and bottom. I did not try to duplicate that shape. I just created the sleeve to stay well (~1mm)below that saddle shape so that it would not interfiere. I also tapered the ID of my bushing for ~ 2-3mm top & bottom for more of a venturi shape- that would be hard to show with pics. When the sleeve is in place, you drill the cross holes so that the hi & low needles can go thru the sleeve. I then pressed the "now finished" brass sleeve out for a brief deburr of those two new cross-bore holes (slightly different sizes as I recall) and reinstalled.
The fairly tight but free fitting (within a drill size, you could say!) cross-bore holes are the real keeper that I trust so that the sleeve can't come out partway and jam/interfere with the normal rotation of the carb barrel.