Hi Mike,
the Pogos, Do not rotate or wobble at speed, they go in the direction the aircraft is being pulled or pushed this is because of the sweep back angle I made them. The benefit in doing it this was is that the you don't need to have it sprung. I designed it using the principal of the full size, where it can rotate freely, there is no need to lock it in place. There is enough excess on the end of the Pogo to prevent it failing out by accident, it as soon as the wings lift 10 or 15mm the spring will eject the pogo. There is also a slight amount of free play in the Steel / brass tube combination.

The strut doesn't need to only be longer but the sweep back angle need to be more, so it's technically held in place by any forward / lateral movement, this I discovered also by pure accident because I made them to long and cutting them shorter again would have been a pain so I bent them further back. The advantage of this is that is takes hurdles in it's stride, obviously to a point though.