Nice parts, could use some of those 
How fast you can plunge into the material (G1) is limited, however moving out (G0) can be as fast as the setup permits. I’ve used the original Z-motor, tooth-belt with 25 teeth on the z-motor and 20 teeth on the c-beam side. The c-beam has a lead of 2mm, times 4 treads = 8mm. The pulley reduction giving me 2 more mm, i ended up with 10mm per motor rotation. My Z moves max 180mm/min = 3mm/sec (for some reason translating to F188 in g-code)
I could easy see that speeds up to 600mm/min could run well, not for plunging in, but on the way out.