After arguing on point b for two months and getting fired, 1885 actually found that our robot's mechanisms allow for plenty of ball storage. We have no 'devoted' place to store wiffle balls, but because of how they travel through our robot, we found that we don't really need extra storage.
Unless your bot is centered around getting all of its balls in the outer goal, in which case you'll probably want to store around 30 balls to comfortably win every game (DE's max score didn't break 200, if I recall) without the use of the yellow ball, then don't worry *a ton* about ball storage. If you can hold a rack and your 8 preloaded, you'll do fine.
(On another note, I'm still employed in said company, thankfully).
Best of luck to your team. ^^