I folded a cardboard W with return wings at the tips and squashed it flat, then run a Stanley knife through it at an angle. That angle is less than the angle you want the cab to finish at....
Back out at uniform angles and you have a wedge. The back of the 210 cab sits on the floor and the W holds up the cab.
Use cardboard from a double skin box and cover it in 50p worth of duct tape.
It can't collapse by spreading to a wider W without getting taller and lifting the cab. The front would have to get closer to the back. Quid pro quo it's rock solid until overloaded and crushed. You're welcome.