'The magical brain'???
If I'm so smart, how come I can't figure out how to shoot better?
Anything that you shoot in a match that's designated 'Smallbore Silhouette Rifle' (Standard Rifle) goes into standard rifle scores and classification. It doesn't matter what rifle you use as long as it's legal for Standard.
In order to get a Hunting Rifle score for classification, you have to shoot in a Smallbore Hunting Silhouette Rifle match with a legal Hunter Rifle.
However, AFAIK there's nothing preventing a club from holding both matches simultaneously. We do it all the time here. You sign up BEFORE the match for either Hunter or Standard. In fact, many here shoot both rifles, alternating from relay to relay. (Your rifle still has to meet the requirements for the class that you're shooting.)
I've never heard of a match approval that was only valid for one venue. I guess that it could be done if the match director sent a match program to NRA that was specifically for a single type match...but I can't imagine why anyone would do that.
MM: Ask the match director if he requested approval for some reason only for standard rifle. Unless that's the case, ask him to run a Smallbore Hunting Silhouette Rifle match concurrent with his Smallbore Silhouette Rifle match and allow those who have legal hunter rifles to shoot them as hunters if they want to enter that way. (He shouldn't, naturally, allow people to wait until AFTER the match to decide whether they'd shot Standard or Hunter.) ;-)
I can't see any reason why he'd refuse -- there's almost no more work involved on his part.