The sp140 comes with batteries specifically designed for it stick with those.
I have a few dozen cycles on my 6s Bonkas and there is no hint of puffing. I’m charging them at a very slow rate - 3.0amps it takes all ###n day. And I’m charging to 4.15V per cell instead of 4.2.
My RC airplane stuff never stood up so well.
I do not have my Bonkas with me…been flying my Tornado…my X4 throttle cable shorted out (very exciting!)…and I am in the process of building a new cable using 24ga silicone wire, shielding tape and wire loom. I am sure someone in the community will be glad to get the measurements to you. This is a great community!!! BTW:. The throttle cable is a part that needs to be almost bullet proof…I know now from experience!
Just measured my 6s Bonkas. They are 21cm long by 6.6cm thick by 9cm wide.
The long dimension does not allow for wire clearance on one end. That’s just to the end of the plastic shrink wrap. The wired end is also a few mm thicker due to the connections inside that wrap so perhaps 6.8cm
I would guess the 7s to be another 11-12mm thick so perhaps 8cm by 9cm by 21cm long