@Andy1 My Rotary is a 4-jaw with 600mm (just under 24") between centres and a throw (maximum diameter of workpiece) of 120mm (just under 5") - so the centre-line of the axis is about 60mm (about 2.5") above the bed. The 600mm is purely down to the size of my machine along the X axis.
I don’t want to swap Y for A. I have a permanent A, so don’t need to do that. What I was pointing out in my comment was that Sienci do want to offer Y swap A and permanent A, and they seem to have found a neat way to do that.
My setup is to have the Rotary axis permanently mounted on the CNC bed (bolted down), I don’t have the space in my workshop for anything separate. Plus, on the ShapeOKO 3XL there is ‘dead space’ where the X gantry can’t access - when X is fully to the back, the X beam plus the front-to-back depth of the Z axis leaves an inaccessible area. My Rotary is mounted just on the edge of this area, so I am not losing much usable table space on the machine this way, and get the Rotary permanently mounted.
I believe the original post you refer to is: First Tests on the LongMill Rotary Axis Add-on