We met Erin and her mom at Paralympic Sports Day, sponsored by Seattle Adaptive Sports. Her mom thought Erin might need better upper body support. Ironically, we ended up addressing other issues that seemed like low-hanging fruit, and which in turn improved upper body position.
After removing uncomfortable foot straps that didn't meet goals, an unused chest harness, and a repaired joystick handle that didn't allow for wrist support, we fitted Erin with an Evoflex®, small U-shaped joystick handle, and Ankle Huggers®. Her chair situation still needs work (a new Permobil order is pending), but meanwhile, she looks and feels much better!
A few days later, her mom reported that she is "bragging how comfortable she was with her new joystick. I personally think that cushioning on the seatbelt is awesome, too."
And that's why we do postural support.