Got the gantry assembly started. Just a couple of 2 x 4 x 11.75 (gantry feet) at the base which are screwed to the drawer slide. Each vertical support of the gantry is a 2 x 4 x 20. I used 2 pieces of mdf one at the top and one one the front of the 2 x 4 supports. There was a lot of play with how much the feet were able to move independently of each other. For those that don't know this is bad. I have since taken a piece of a shelf mounting bar (that a shelf bracket would fit into) and bolted it to the 2 x 4 supports. This did greatly improve the feet staying together but in the world of the thousandths there is still a lot of play (+/- 1/8, it was +/- 3/4). I still plan on using a threaded rod on one side of the gantry to move it forwards and backwards (what I what to call the z axis), if I am unable to get better results on preventing the play, I may just switch to a belted system for the z axis.