Giant 20' x 3' x 2' router build

[JAZZCNC]

There's nothing between the motors. I would definately go with the digital drives thou in My experience I'd go with EM806 rather than the DM856 as they are worth the extra. They have better resonance handling and stall detection and just seem to run motors that bit smoother than the DM856.

With the rack I'd go with sprung loaded as it keeps backlash to a minium and lowers rack wear. Problem with fixed is you need to be very precise with rack alignment and pinion tension/engagement otherwise it wears quickly and can stick or bind causing motor stalls.
Sprung loaded is more work but more forgiving and if done correctly gives better backlash and longer life.