Great derivative. This is the direction I'd have gone if I wasn't having to print to a smaller bed.
One thing I noticed in your picture, the order of parts...
When storing the unit, I keep the parts arranged as pictured so none of the parts get lost. When using it, the big nut sitting right under the camera goes under the sled. The idea being that the camera sits directly on the sled and the
nut screws up from underneath to tighten it down. Since most cameras can only accommodate a little bit of the bolt, you screw the bolt into the camera as far as it will go, then tighten the nut to secure it.
I'll make a note of this on my thing as well, I'm not sure how I overlooked mentioning tha
That should reduce the wobble in your shot.