To be honest, weather didn't premit flying for last month or so [&o]
but with temp around 15 C or higher I can get full flying day with single charge
on Sanyo.

I think anything larger than AA size would get too much weight penalty.
Maybe trying 1800 or 2000 mAh NiMh in same size would be better ?
Had them on Magic (nearly same servo setup) and they lasted forever.