If you will permit a non-official reply:

If you change the sailplan in any way so the boat no longer measures in under the original one design rule (Stealth R), and the sailplan dont measure in cleanly under F16 rules either, it just dont measure in. Mixing sails from the old and the "new" sailplan is not something I can find support for in the rules and personally I dont like that idea either.
In my opinion one either goes F16 and is compliant, or one stays with the one-design concept. Mixing and matching belongs to racing under non-standard SCHRS ratings.

The 3cm extra on a grandfathered boat is in my private opinion no problem. I'll be happy to race you.

Just my humble opinion..