Ever tried getting one of these? -->
http://www.batteriesamerica.com/lithium_polymer.htm
I think the smaller models (LP145 and LP190) would fit on a MT chassis, maybe even on a regular Zip or SE. And they sure are light-weight. Only problem might be the charger. I'm no expert but I don't think the controller charger can handle li-poly batteries.
Any thoughts?
By the way very nice collection

I'm still pondering if I should import a MT or not o_O