Thanks for all the great input guys. I referred the Petzl CS guy to the chart I referenced earlier, and he changed his tune, stating "I was looking at the Tikka XP, yeah the Myo are not compatible with lithium." So, that issue is resolved, and I think the Petzls are out for me. I really like the performance of the lithium batteries (even in warm weather), so...
Dan, thanks for the firsthand Apex info. Bradford's right on about the reason I'm looking at the Extreme.
CK, thanks again for the awesome info. I'll check with the PT folks about using the Apex Extreme with only 4 batteries.
MM, that HP10 looks a lot like my BD Icon. I've tried to reconfigure my Icon so that I could use it with the battery pack around my neck. The wire running from the lamp to the battery pack would need to be maybe another 10 inches long. You wrote that you "put a longer cord on it". Is this a simple process, or did you need to splice wires, etc?
DW, by "lots of light", I guess I'm looking for something similar to my Icon, which (according to specs) maxes out at 100 lm (more would be fine, but not necessary). I'll check candlepower forums on the LiIon/LiPoly stuff, as well as info on modifying my Icon. I'm a little leary to be cutting and splicing wires...but it's certainly worth checking out.
Anyone here have any specific recommendations on LiIon/LiPoly options?
My other option would be just using the 8 AA cell remote battery pack, Princeton Tec bicycle light I already have, and just making a strap system for it. This wouldn't be too difficult. But it's probably 5 or 6 years old, and I'm not sure what model it is...and I'm not sure that it would work with lithiums. It does work really well with Alkaline and NiMH cells, though, so maybe I'll do a little more research in that regard.
Thanks again, everyone.