Looking promising!
I built a monster printer a while ago: 15" cube print volume. The KEY thing for big prints: get a volcano nozzle! I run a 1.2mm nozzle. Yes, that's only a little smaller than the 1.75mm filament... When you want to make BIG parts, there's not substitute for massive volume!
Sneaky slicer trick: do the infill every two or three layers. This makes the surfaces look a lot better and doesn't slow it down TOOOO much.