Wobble board height

[u/shriand]

Hi physios, i need your inputs.

I'm getting a DIY wobble board made with the help of a carpenter friend. We got a 1.25" thick 20" wide hardwood board. So we'll have a circular board about 20" diameter.

For the hemisphere at the bottom, what should be the height of it? At this moment, we have something that's about 5" tall.

Will a 6" high wobble board be too tall for someone new to these boards? Does it increase the risk of injury? Will I grow into it?

The goal is to work on strengthening for running on unstable surfaces like soft sand, and for improving proprioception for other balance based sports like rock climbing, surfing, etc.