I mounted the floor in the box today and got some of the bolts countersunk.
It's made from 3/4 particle board and is very strong.
Under the floor I will mount another 3/4 plate where the casters will mount
and this will give more than enough strength for the casters.
I didn't notice but my aluminum channel is 2x2 instead of 1-1/2.
Now you would think I would have noticed this ;o)
I need to get some more bolts and the threaded rods for the corners.
The only thing I'm not sure how to make is the cable lift for the top.
I need to find out, How you attach 4 cables to a eyelet so the crane will
have something to hook.