I’ll probably place the cells as close to the center as possible to shorten wiring and to have a better weight balance, with screws to keep them in position.
to have them inside the frame allows me to protect them from damage and to save space and weight of battery support.
I’m a bit confusd regarding AWG and ampacity, because motors are 25A rated and arrived with 18AWG wire, but according to wikipedia 18AWG has 16A ampacity, am I reading wrong the table?
https://en.wikipedia.org/wiki/American_wire_gauge
considering the quadcopter maximum draw of 30A, which AWG should I use for wiring the battery?
Even the official data sheet says it’s safe to run them at 20A. You will be fine.
which data sheet? but shouldn’t it have an ampacity greater than 30A to be safe?
First thing I thought of when you said battery and Baba 
thats a LHB 30q pack, grandma is packing heat 
Finally here is the diagram (i divided the 2 arms to simplify reading), is it right?
I’ve never seen a more confusing battery diagram 
Maybe it’s just my inexperience
Also I think you’re drastically misunderstanding how weak a 6s2p of liion cells are
I think this is because of the shape required, what do you mean with weak?
The amount of amperage it can realistically supply is low, in addition to mAh
Most packs are larger than this, but I wouldn’t know your list of necessities/wants 
using HG2 cells it will have 40A of constant discharge current and 6000mAh of capacity, my quadcopter will draw a maximum of 30A and higher capacity would be too much heavy.
regarding the diagram, how would you do it?
So when one has batteries in parallel the constant discharge is added? like the capacity?
