========================== Yes, Battery Energy Density and their High Cost is a Problem, also People always wanting more, more, more HP! To get a Good Price break, like $1 per Cell on the Battery's you have to buy a lot, like 20,000. Same battery at Battery Stores $5. There Lazair Flew on (2) 5.5hp Chainsaw Engines, 11hp, was soon upgraded to (2) Rotax 185UL's at 9.4hp equaling 18.8hp, then they want to put even Higher Hp Electric Motors requiring more Battery's. Just put (2) 10hp Electric Motors with Carbon Fiber Props on it, and enough Batterys for Minimum 1hr 15min of Flight and be Happy. If you can have even more Flight Time so much the better. If you can't provide that minimum Flight Time, then go with a Gas powered engine. Using (2) Honda GX200's making 10-15hp with an Ace Belt Drive is still the best Bang for the Buck. If you already have (2) Rotax 185's, your better off just Rebuilding it, and Upgrading them for a little more HP if you need it. Yep, that's 8+ Years of Lost Sales of his Lazaairs. Build what you can Sell now to make Money, then do R&D on the side.