It's funny, I don't have massive hands, yet I've managed OK on 6ers since I first tried them.
When I was at Art School, one of my class mates, who was 6 foot 4 and had massive flapping hands, could barely get his hand round the neck of the 6er I had at the time.
I think your hands just get used to it, the muscles adapt, stretch and get stronger.
It also means anything smaller, 5s or 4s feel comically small when you go back to them...
If 16.5mm spacing wasn't available, it wouldn't stop me playing 6 string basses, I'd just have to get used to whatever was around 😎
Eude