I'm going to preface this post by stating that I am not a member of the N-SSA, so as to the extent of scrutiny that their artillery inspectors display when examining pieces of ordnance for first qualification, and later random inspections at skirmishes I really couldn't tell you, but I'm going to do my best to answer your question. Wait a second, I'm answering my own question here, and there's something not quite kosher about that, but then again neither am I.
Here are some quotes from the N-SSA Artillery Rules:
18.5 ARTILLERY PIECES, EQUIPMENT AND AMMUNITION
"Artillery pieces and equipment shall be inspected by the Artillery Ordnance Officer or his
deputies the first time each piece is registered. Thereafter, they shall be subject to spot
inspections. Ammunition shall be spot inspected at each skirmish in which the piece shall
compete or demonstrate. This inspection of ammunition shall not be scheduled and no
notice shall be given. Violation of regulations with regard to charges and projectiles shall
result in the withdrawing of registration to fire at that skirmish. Any appeal in this case
must be presented to the Board of Directors as an official protest as prescribed elsewhere in
these rules."
"All cannon, either fullsize or scaled replicas,
must maintain the same construction and ratio to the original in all components, including the carriage, bore and exterior of the barrel."
"Replica mortars must utilize a bore and chamber conforming to the dimensions of the original mortar. No auxiliary chambers will be allowed. In addition, the bore must be at least 4.5 inches (12 pounder) in diameter,
and the carriage or gun mount must conform to the style of original Civil War mortars."
Knowing this, I would guess that using British 12 spoked artillery wheels would not be a good idea, and furthermore, it would probably be in a members best interests to match the original equipment as closely as is possible.