Where did you get the plugs for the balance portsI've been charging my Volt Modules in parallel for several months now with no issues on my Tomberlin Vanish UTV - my top balance cheap BMS simply has a parallel harness that plugs into the two balance ports. I've seen this done with as many as 6 modules. The only thing to watch out for is before plugging it in make sure they start at the same voltage so there isn't a huge surge of current to balance them upon plugging in!
And do you have the pin out?
I have the same batteries but without bms