I can confirm that the use of circular leather punches was original
Aeolian practice.  My Duo-Art still is running on its original rubber
cloth (which is perfect -- a single-ply attached rubber-side inwards).
Its hinges are covered with circular punchings about 1.5" diameter.
I have a spare motor with original cloth that's got a strip of leather
to cover the hinge area.

Aeolian certainly did make a number of variants of these 6-pneumatic
see-saw motors.  There are some early thin-but-tall ones, then the
familiar shorter design in its earlier incarnation with a 3-section
crankshaft so the slide valves are connected to the motor-pneumatic
arm, and finally ones with a 6-section crankshaft where the slide
valve travel is reduced by connecting them to a separate crank section.

My Duo-Art with original circular leather punches is the latter design.
I've never measured to see whether the span varies!

Julian Dyer