Good spot for bonks.
PX to GT is a big weight and size change. The XR feels noticeably lighter and more playful than a GT. And still the GT is my go to. In the car world, there is a saying “there’s no replacement for displacement”. The equivalent PEV saying would be “there’s no replacement for voltage”. This is especially true for a onewheel. The power in my hilly area is too comforting. Also the GT makes curb nudges super easy (lean back, pop your hips forward when the wheel is about to touch the curb, level the board as it starts to climb the curb, done). The more you ride the GT, the less you’ll want to ride the PX. Unless carrying the board is a factor.
I bet your foot angle is contributing to knee pain. Gotta try a more square stance.