nooo they wont be solid.. the urethane comes in a few different wobbleyness's(nice word)(technical term "shore")
the shore of urethane that I am looking at isnt that solid.. it actually is quite "floppy"
I think the pic is a bit missleading cuz it gives you the impression that the stuff sets solid.. but it doesnt.
thanks for the feedback tho..
I will post a few pics when I do it.. HERE
is a link of someone who has done it allready