I also went with the kress and made a z-carriage similar to yours. Mine is for the sorotec mount I posted above and is (also?) based on the universal mounting plate from inventables, but I milled it out of a 5mm aluminium sheet, which took the whole day with 300w spindle 
One difference to yours, is that I placed the delrin nut holes between the top and middle holes, where I mounted the wheels. This configuration allows the Kress spindle to go all the way down to the wasteboard.
I haven’t it realy tested, because I noticed that my x-axis is slightly tilted to the front, and I also want to stiffen it a bit.