Does anyone know if there is any reason a Phil wood sproket wouldn't fit on my Formula hub? I think Phil Wood hubs are a different size but I'm not sure...anyone know?

There shouldn't be any reason it wouldn't fit.
Are you trying to put it on the free wheel side, maybe?

I haven't gotten one yet...I'm upgrading my components frm no-name to sugino etc and I thought a phil wood sprocket would be a good addition.

Oh, I see. I misunderstood the original question.
I know of no reason why they shouldn't work together.

got a phil wood sprocket and an iro (formula) hub. fits perfectly...

a phil wood lockring, however, will not.