Aright Dave, I froze my fingers off and ran my Sportster .20 today. It was 29F outside.
APC 9x6 @ 11,280rpm
APC 10x6 @ 10,020rpm
MAS K 11x6 @ 8,790rpm
I don't know what size the carb is, I'll measure it later. I used the same fuel that I've been using, though I think these little bushing engines might need a little more oil. 25% oil would probably be better than the 20% I was using today. It idled down to 2,300rpm and throttled nicely. I think the eccentric screw doesn't allow it to go quite rich enough down low, but it would recover pretty good anyway.
Edit: added video.
http://youtu.be/dSP-DnOP77Y