1 you lose 1/3rd the tube length because a slot is needed for arm linkage.
2 skinnier longer tubes great, less effort needed, how long can you practically go and how many strokes do you wanna do?
3 bigger diameter tube brings up the required force exponentially to achieve same pressure.there is no system in place to reduce the human effort put forth( minus supercharged pumpers for less strokes- see rons idea)
4 rons supercharger dual outlet pumper idea is amazing..(to me)
5. Ac pumpers,indys, and such are not what dan was goin for in his thread i feel.
6 my friends will not be impressed with 9 mm pumper if i have to pump 100 times per shot..hence some need is there for more practical swept volume and piston diameter is the unsolved answer.( or my goofy 3 speed transmission downshifting as effort increases in 1.25 bore tube.)
"i never was much for book learnin"