I saw your large printer @Chad_Nuxoll and raise with our! (me and my friend) - 700x500x500mm (~27x50x50in), print area around 440x300mm. Double E3D bowden hotend. Still working on Z axis…
That certainly look like you’re doing things properly. How are you adjusting the hotend’s height, though?
hotends will be mounted by thinner part at the top of alu heat sink - it will be possible to adjust them vertically
What size nozzles? Nobody wants to wait for a 300 hour print. 
at the beginning regular ones: 0.4 or 0.5.
We still don’t know how to heat so huge print bed. Silicone heater or myriad of power resistors?
Nice. I’m surprised the bearings in the middle of the shafts are necessary.
Omega heating elements has some nice silicone pad heaters for a reasonable price
@Daniel_Joyce could you post some more details? link?
@Jarek_Szczepanski We’ve used their kapton and silicone before: http://www.omega.com/pptst/KHR_KHLV_KH.html
Nice. I think given the weight of your X axis, you should consider 2 Nema 17s driving the Y shafts. Either that or a Nema 21.
Might also be worth considering synchromesh instead of belts as it’s much more resistance to stretching.
Wow i cant believe i missed this post looks good hopefully the hot bed gets figured out