Became aware of the fact that my JM930 can be "ghost loaded" to have an extra round under the bolt.

Wondering if this would violate any rules, or if the tube still only holding 8 rounds would be ok.

Yes, ghost loading is generally OK, but you still can only start the stage with 8+1 in the gun. In your case, I think this will make ghost loading irrelevant as your gun can accept 8+1 without having to ghost load. About the only folks who really need to ghost load are those who run tactical guns (e.g. a Benelli M1 with an 18" barrel that only takes 7+1+1), and of course Open Division shooters who have no limitations on capacity.

That's the info I was looking for, thanks.