I use 81.5 mm for multiball and it's at the very limit of what I can use. I have small hands. : )

> might be worth starting with 3inch. <

I strongly disagree.

I'd recommend using 2.25 to 2.5" balls to begin with, regardless of your hand's size or what you think "looks good". Snooker balls or billiard balls work fine and are much cheaper than acrylic, especially if you get used balls.

You'll acquire sets of acrylics in various sizes eventually, but why spend that kind of money when you don't know if this skill will interest you in 6 months? In the meantime, assuming that you'll learn fast enough and be good enough to perform in public with your first set of palm-rollers is, uh, presumptuous.

Continually using a set of rollers that are too large for you at your current state of ability is asking for tendonitis problems that may terminate any interest you have within weeks. Ibuprophen may help, but it won't stop you from being crippled if you move to fast.

Increase the size of your balls very slowly, and only after you have developed the stretch and strength to handle your *current* size easily, whatever that size is, for at least 30 minutes at a time. When your most difficult multiball moves are easy, and everything else is fluid and rapid, only then can you safely consider moving up to the next available size of larger balls.

YMMV, but if it doesn't, you've just screwed yourself out of doing *any* multiball work for 6 months to a year.

With multisphere, moving up or down a size effectively starts you back at the beginning. You have to reteach your hands everything because with smaller spheres you fingers tend to curl more as opposed to larger spheres which require more of a stretch. I've found that it works best to start with whatever size takes up pretty much your entire hand when holding 3 in a triangle. If you can hold them, you can learn to spin them. You just have to play for shorter periods of time while you build up your hand strength. It's a precarious line of practicing enough to progress and not going so long that you hurt yourself.
Multi is a completely different animal than single. It's much easier to change sizes with single or one in each hand. I started on 2.25" spheres for multi, then realized that they were just too small. Even spinning two in one hand without clacking was a challenge when I first started with 2.5".
I haven't decided yet if I want to relearn it all with 3"s.