Out of curiosity - can you juggle four balls?

I can, but I wouldn't describe having two two-ball capable hands as being half-way there. If forced to put a number on it, something like 20% is the best I could do.

I may try that. I can do two balls in either hand already. I just never tried doing it in both hands at once.

Strangely even though I'm right-handed I feel more comfortable juggling two in my left hand. I also bat and golf left-handed so sometimes I wonder if my parents forced right-handedness was on me.