Hello Nikos,

I fly with 8s drive set and 4500 mAh TF 20C a motor running time of 8 minutes. After this time, I never need max. 3500 mAh in P11/F11. mso I have a rest capacity of approx. 20 % at the batterie for a longer life.
The 8s drive set have with APC 21x13W or Delro 19x14 5750 rpm; that´s approx. 200 rpm less then the 14XL. I prefer the Delro because I think, it´s over all
(performance at each wind conditions, handling) the best prop for Hacker competition 8s and 10s (14XL).
But you have a much lighter model, because 8s save approx. 250 grams! Over all, you have the feeling of a little more power. Please believe, if I had the feeling, that 10s are better, I would fly 10s.
Add. you can change at storm-conditions with 8s to 35 or 45 C batteries, which give a lot of more power again . With 10 cells, this change is not possible because of weight limit at the very most models.
To get 9 minutes motor running time with 8s drive sets, you should go to 5000mAh batteries; the Top Fuel 20C 5000 mAh is only 60 grams heavier like the 4500mh. The slightly better tension voltage under load should eliminate this 60 grams more weight with the same felling of power.

The batterie fixing ( please have a look at any older attachment-pictures to learn the system) is a very nice, very proven and lightweight solution. But it´s not flexible for different size of batteries.

Bruno