if i may suggest, a part with your form factor that is similar to the feline rover life support module would be exactly what's needed.
- about the parts splitting, i took a look at the cfg files for your parts (i'm an amateur, i don't really know what i'm doing),
i noticed that the breaking force numbers were set to 50, while a lot of other parts from other mods had that number set much higher up to 9 times as much,
would that cause the splits i'm describing ? again i'm no modder, i just sometimes read the cfg.
sorry, didn't include this in the last reply (too sleepy)
not a specific part, just the over all weight of the craft struck me as too heavy for it's size, i'll describe the plane i tired to build with your parts:
cockpit with docking port, extra crew, cargo small, 2 cargo large, fuel tank, and the tail tank (the one with 3 points) , 3 vector engines, and the wings.
very basic, i just felt 50t was a little too heavy for that.