Try playing your accordion through a guitar amp...set the gain mid-way.
I guarantee you'll put in about 30% of the effort on the accordion to get a decent sound level compared to acoustic only pumping.
Make the amp do all the work, then you can concentrate on things like minimal bellows action..if you start pumping the accordion too hard you'll blow your ear drums and maybe the amp !!.
IMHO same applies to guitar...I've found I play much better playing my acoustic/electrics through an amp....seems like I can concentrate more on technique, embellishments, etc.
BTW. My shoulders are shot from arthritic clavicle progression and bursitis..about to go for right shoulder operation. Left side was done a year or so ago. Surgeon says something like..'stay away from those ****ed accordions'.LOL