I'll second the suggestion that you get back in using NiMH 6v packs.

That should give you the torque you'll need. Just remember to size your packs LARGER than what you would have used with 4.8v packs.

Ameyan's suggestion of 2100mAh packs is a good one.

I've used the OUTRAGEOUSLY EXPENSIVE ( 12.00 each!!! ) 2100mAh LiFe packs from Turnigy. [link=http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=28650]LiFe Packs[/link]

They are light enough that I can afford to use redundant packs in .40-.60 size planes.

They do require a LiFe charger however.