tessmar

Thanks, Coolbean
I used the brantuas.com/ezcalc calcultor. It does not have my exact motor but from the Electrifly site the Graupner #6309 seems close. Likewise the closest battery to mine seemed to be the Sanyo 2000SCR. This baseline does indeed match pretty well to the flight times experienced with the plane (4 minutes or so).

Changing the calc to a Kokam 2000 Li-Batt with 2 cells gained 20+% to 4:53. But the prop thrust and motor revs drop and I don't really know what that means. However, leaving the stock motor and battery and changing from the stock 9x5.5 prop to the GD600 gearbox at 2.5:1 and a 10x8 prop increase the time by over 150% to 10:35. Again, prop thrust is lower (as are prop revs, but of course not motor revs). Even bigger gains appear with a 3.8:1 ratio and 10x8 prop (with even lower prop revs and thrust). This winds up at 12:56.

Unless I am not understanding the calculator all this says I should try the gearbox and prop change (at well under $50) first before investing $150 or more in LiPOs and a new charger.

I'd really appreciate your thoughts as well as saying thanks for the help you have provided thus far.