Ok, I think I figured out what my problem was:
The big loop I used before is in green, and my idea was to use the red path, killing bugs BA and BC then turning around and killing them again as they respawn. This is what I did with the warthogs, but they were closer together. These two spawn points are too far apart, I can't kill bug BA then BC and clear out fast enough for BC to respawn. If possible, this would result in a kill rate of about 2.2 sec.
However, I can still get 2.2-2.3 with a three-point pattern where I kill one enemy on each end and one in the middle as I move. This would suggest BA-BC-B8-BC-BA... If I could fit in F6 as well this would be even better. The bugs move a lot and sometimes it helps and sometimes it's a pain. I know I can get about 2.6 with BA-BC-B8-BC-BA-BA-BC-B8... Anyway, making some progress, once I figure out the pattern it will be pretty easy to carry it out.
Here's my spreadsheet (openoffice.org) with levelup numbers from my tests in case I try to reference it again.
http://home.comcast.net/~f_amoroso/leveling.sxc
Oh yeah, I have thought about doing a non-warping run, it could be interesting. Of course I'd have to figure out the leveling all over again, but it could be an interesting look.
UPDATE: I've prototyped a pattern up to the experience amount I need (232), and was about 20 sec faster than my last test. It looks like the best policy is to maintain some flexibility to deal with quirks in the spawning. I was doing BA-BC-F6-B8-BC-BA-BC... with some occasional changes. However, next I will try BC-F6-B8-BC-F6... which will probably not be a stable loop but perhaps close enough.
Ok, have a general plan now, but there are still some unknowns. It's definitely possible to do BA-BC-B8-BC-BA-BC... but if I can cram in F6 then it's even better. However, this is a tight loop as it is, and there are some major problems when the three bugs spawn in unfavorable locations and or roll away quickly. It looks like I can vary their movement by changing when they come onscreen, but the location is trickier. I don't have a lot of room to manipulate things as I am constantly in a tight race with the spawn counter.
The bugs seem to be able to spawn a over a pretty wide range, for example BA can be at the upper left or lower right of that T-junction. When he is at the lower right, I can get some extra time to stabilize the loop. Well, I'll see if I can manipulate the spawn location, otherwise I might end up doing something more free-form but the general idea will be the same.
