Thanks pasusan.
For me the slippery is not the issue. It's the weight!
UPDATE:
I have seen on another Forum that a spring has been used, installed / attached to the horizontal bar and the upright bar. so to lower the tire you may have to push down! But to raise the tire the spring takes much of the weight and pulls it back into upright position.
At least that is the theory.
I'll be going to an automotive (springs and shocks, etc.) shop this week to see if they can do something like this for me with a heavy duty spring.
PS We use our unit actively and when on the road I'd like to have ready access to the entire rear space.
Morden