Hey Derek, hey all,
we ended up choosing the Onefinity Journeyman, but one machine that this would also apply to is the cnc-step High-Z. With a size of up to 82.7″ × 41.3″ (6.9′ × 3.4′) and its open, extruded aluminium frame, I think this job would have been possible with it too.
I think that there are a number of machines out there that use this simple concept of an open extrusion aluminium frame. However, aside from being open, it is not comparable to the Onefinity as you either built a base or table for it or use the QCW frame which is also different. The question is what about the stiffness of the frame, but I think both types of frames need to be adjusted in their final working position.
By the way, it was very hard not to buy this machine as it also has ball screws and with its plain bearings (instead of linear ball bearings) on steel bars it even mills steel, and with its power chain cable management (which of course costs) it is very convincing. It also has a 43 mm Euro mount (which is still missing on the Onefinity CNC) that allows for a variety of single-phase (non-VFD) milling motors such as AMB (former Kress), Suhner, Mafell, etc., but spindle mounts e.g. for Mechatron are also available (this machine was already discussed the other day here and here).
Understandable. But I would have liked to see it too 
How thick/stiff was your squaring jig for the Onefinity and what was it made of?