Guys, i had a moment 
Brilliant idea came, tested and its fantastic. I have used M3 threaded rods to slide on the modules. Works great. You only need 2 aluminium angles to mount to the board and its flexible. If you leave a small gap between modules it will flex good both ways. 
…and you can have more of them for strength. I paid 0.50ct/m
A little reinforcment of the channel might be necessary, maybe test it on your shaking table first But the ide itself is great
You suppose to mount them as per second photo. Should be tons of strength
Don’t underestimate the vibrations working on the heavy (when filled with cells) cases. The threads might scrub the petg and finally break it. I just tested the stability of the spot on a broken case with a punch on a flat screwdriver -> broken, so it might need reinforcement and maybe only threads on the ends of the rods.
Sure needs road testing. I am going to mount my bike battery like that but vibrations are far milder
Nice!
In my latest iteration, I am using 3mm carbon fiber rod in similar fashion. I say similar, because instead of holding the m3 rods on the edges of the box, it holds in the middle. This allows for max flexibility. There is a piece of 1mm tpu slice in between each module. In addition, each module is mounted to the board using a tpu mount.
Struggling with my battery right now. Never used. All cells were brand new from @thisguyhere and at the same voltage going in. Each group is at 4.19 to 4.2v except one that is at 4.08
I am getting a green light on my charger though so I cannot get the single group to go up
Full pack reads like 41.5v
Do I need to discharge it a bit and re balance charge or?
I have those cheap BMS too and they slow to balance. Just give it time or if you have a hobby charger, charge each parallel groups to full individually and then will be fine.
Will it still balance and charge even if light on the charger is green?
I need to buy a hobby charger for sure
You can take a multimeter and see if balancing is happening. Check over 15 minutes duration.
Yeah I don’t think anything is happening 
just sits at 4.05 while others at 4.18
You need to manually balance it. 0.1v is too off.
Recommendations for hobby chargers are appreciated,I don’t have one and I’m sure that’s really the only way.
If you wanna do it for cheap. You can use these Tp4056 and charge them up slowly
TP4056 Charging Module 5V Micro USB 1A 18650 Lithium Battery Charging Board with Protection Charger Module https://www.amazon.com/dp/B071RG4YWM/ref=cm_sw_r_cp_apa_i_dA6WCbBPQF72X
Would I just wire the + and - to alligator clips and charge the p group?
Yeah. Or use jumper wires and stick them into the balance wire jst connector.
Surprisingly I had one from a remote build