Any question answered...

^^

The general rule is divide the number of holes by 9, what ever that number rounds down to gives you the maximum number of crosses.

So 24h / 9 = 2.6 = 2x

How deep is the rim?

You could always try half radial to mix it up.

Its a 50mm alloy rim. Rigid.

I'm pretty sure I've got a 24h wheel built up 3 cross...am I imagining this?