Let me guess, you have printed separators..... Does it help? I am finally recognizing that everything I knew about IC is just taking up space in an aver shrinking memory bank. Battery cooling is a real art form and a lot of our planes really don't do it very well, especially conversions. Anybody that can feel 1 gram of tip weight in wind has to have a better battery box. Pictures? or not.
Some pictures are at
https://stunthanger.com/smf/plotters-and-cut-files/what-have-you-printed-lately/ .
My P30Bs end a flight at just over 3.5 volts/cell. As I recall, they get to about 120 degrees F. At lower voltages internal resistance, hence heating, goes way up.
I didn't like the way people were making Li-ion batteries. They wouldn't fit in my airplanes, they were of inconsistent shape, they were covered in heat-shrink blankets, they had balance cables of no use in flight, and they had unnecessarily heavy and long wires. Printing the end caps (Brent's idea, I think) allowed space for cooling (not as necessary as I feared), allowed the balance connector to be mounted on the battery, allowed mounting provisions to be printed in, and made the overall battery shape consistent. Consistent shape made mounting them easier. I am still figuring out better ways of holding them down, and the closer tolerance of printed parts really helps.