RE: what size battery pack
Just consider that you have a lot of horsepower to "play with" so you can afford a few extra grams (not ounces.. pbecause the differences in batteries will most likely be grams, not ounces (plural) ) of weight. I would go with the largest battery pair that you can afford with the weight, regardless of the number of flights you can attain. The most important consideration is to supply the proper voltage and available current for the style AND duration of flight your aircraft will endure. If you have lots of power, an ounce difference between a lower capacity and a higher capacity will offer more benefits (duration and peace of mind) than drawbacks (weight).
CGr.