Hey Tony,
Note that it may not be wise to use only the minimum dimensions, but that you should allow for some extra space all around, especially if you are building an enclosure (recommended).
The dust boot stands away from the front. If you change to an 80 mm mount to install a 80 mm spindle, this overhang will increase by 15 mm.
The hose also protrudes to the rear, at least if you use a dust boot that leads out to the rear.
Measurements (photos) of PwnCNC v8 dust boot overhang:
(What is the Best Dust Boot for the Onefinity?)
On the left you should reserve at least six centimeters extra if you switch to drag chains later, which means a cable routing more compatible with the permanent motion.
And to the rear and to the right you should reserve some space in case you want to replace the cheap little open-loop stepper motors with closed-loop steppers or servo motors, which can be longer. Note that there is a way to mount the X and the Y axes in the opposite direction, which means Y steppers would be towards front and X stepper would be to the left (and drag chain on the right then). This is possible because you can switch these axes to “reverse” on the Onefinity CNC controller display (under MOTORS).