I fly Scale models in International events. I currently fly a 2.5m span Tucano and a 2.3m Ki-43 Oscar both are using CNHL 12S 9500 packs.
I pared 2 x 7200/6S Li-Hv packs in the Oscar. Loads of power. smaller packs and saved 120grams in weight. Only just enough to complete a 7 min completion flight. I am going to try 7800/ 6S x 2 (12S) to get maybe another 30 second flight time.
Just a word about your standard battery tester. It will indicate a higher capacity as they are mostly set for Li-Po's. You can get a tester that will test Li-Hv as well. Thats what you will need to test the capacity left in your packs.
I have requested 9000 mah 6S Li-hv to test, but not made as yet.
Nigel Nixon UK RC Scale flyer team member.