That's a good question. All of the vintage CPO shirts I've seen have the placket on the outside, but no curved cuffs. The MFSC CPO and denim Utility shirts are the only shirts I've seen like that. Apparently, they are based off of 1930's CPO shirts, which aren't too common, I imagine.
I think I'm leaning towards inside placket on the cuffs. Otherwise, we run the risk of it looking a bit like a jacket from high school marching band?