It looks to be a very tidy and effective design Ralph and no loss of area.
My only concerns are:
1. The thread pitch looks to be very coarse so isn't backlash an issue? It would have been nice if they had used fine pitch threaded rod giving the tidy 1mm movement per rotation.
2. Also, what is the free play in the sliding plate like; is it enough to cause issues when the the dives accelerate?
1. The threads are 1/4 28 (28 is fine pitch) and this works as an M6 size as well. I don't understand why backlash would be a concern for you? Can you explain in more detail?
2. I've eliminated almost all of the free play in the laser mounting plate, which is the focusing plate. Not all of it but most of it. As I use it, time will tell if it remains stable in place or if it moves with rapid X axis movements.
Note: while I can't recall exactly what I paid for this, it wasn't over $20.00. This is probably the best design you're going to get for that kind of money (even tho you can't buy it as a stand alone item).
I agree the whole design should work more smoothly and be nice and solid, but that would add to the cost and add to the weight. From a re-design stand point, I have not put pen to paper or keyboard to QCAD -- but -- I'd like to see some kind of bearing movement on two short rails such that the vertical movement is very smooth. And a finer thread count would be better too as you said. This re-design would be a combination of acrylics and metal. I'd probably also include my laser quick connect/disconnect design that I have already done and was previously using.