Removable cradles is actually very simple.

All the cradles come with a "seat" that will take the axis of the cat tracks. And the diameter of the seat fits the round rollers very well. So lift your hulls up and slide the cradle onto the rollers and underneath your hulls. Some people also clamp or tie down the cradles the the rollers, I don't I just tie down the boat to the trailer and that keeps the cradles in place. But I have excellent roads all around me.

I personally heavily favour Eric Poulsens setup as I think that can easily be homemade and it will work very well. I'm looking to rebuild my own trailer and then it will be like Erics.

Wouter