Needed some Mecanum wheels for my RC project. They're compatible with a couple different shafts.
Your choice on the hub. I used 30% on the "tires"
I printed the hub w/ regular PLA and printed the "tires" in flexible PLA. That gave me a little better grip and slide.
The bearing holes are good and snug. You may need to lightly file them. It's a good idea to have bearings ready to load up as soon as the hub print is done. The warm PLA is less likely to break.
I use a 4x8x3 flange bearings and M4 x30mm button bolt through them. Works pretty good.