RE: Does size matter?
Electric flght is a matter of math. Bigger planes require bigger motors which draw more from the battery. If you size the battery properly you can get any flight time you like, as long as the airplane can lift the batteries.
If you size for 10 minutes on your parkflyer you can size for 10 minutes on a 1/2 scale. Why not? You just need a bigger battery and a bigger motor/ESC.
No big deal, just big budget.