I thought tubeless tyres were invented for downhillers because it means you can run lower tyre pressures and not get pinch-flats. Running at 20 to 30 psi with a tube might see your tube get pinched and it'll go pop, especially the back wheel.
Changing tubeless is a sonofabitch because breaking the bead out of the rim can be hard, way harder than a traditional hooked rim.
