You're welcome!

You lost me........ If the baffle height is 60" max, then how does one extend the internal volume (net Vb) to 70-74"?!

Regardless, I previously noted that since a large baffle needs bracing and cabs usually need some in-room fine tuning, best to make a separate woofer and vent baffle, so 5x5 ft panels are plenty large enough to make the cab from since the side panels need bracing that can double as multiple panel joints.

WRT net Vb, for a given height, width, then obviously the only way to increase it is by increasing depth, though again, Olson's work indicates up to 10.5" regular depth was acceptable, so the theoretical max depth will be a 10.5" o.d. front extension from the wall and the distance from the wall to the corner apex.

Note that room corners around these parts are rarely exactly 90? or perpendicular to the floor, so best to make a cardboard cutout of the ideal size to check at both the floor and at the 60"/whatever height to see what, if any adjustments must be made to the cab's design lest you not be able to slide it all the way in.

GM