One of the best operating versions of the Duo-Art, in my opinion,
is found in the Stroud upright, which has all same-size pneumatics.
All small.  There is all the space for smaller sizes if needed.

In fact, the Duo-Art Concertola stacks that were made out of metal had
three sizes of pneumatics, all Stroud-size or smaller.  These stacks
were introduced probably as early as 1928 (yes, I have piano serial
numbers) and well into the 'thirties.

All the long-play Steinway grands (with the player action above the
keyboard) that I have information on that have 1930s serial numbers
have graduated pneumatics.

The last of the 9'6" Concert grand Steinways was delivered to Aeolian
March 31, 1930.  It was fit out with its stack above the keyboard.
They used the Concertola metal stack with three sizes of pneumatics
(tiny, tinier and tiniest) and it was not some trashy, depression-era
installation.

Frankly, as much as I love Aeolian, I rather like hanging poppets and
using a soft pedal compensation list to accomplish the same end.

Bruce Grimes