1. Should it be an identical glyph to period?
2. Should it be the same character width as period?
3. Should it be centred vertically on the cap height (with suitable “optical” adjustment)?
4. Where a type is “high- (or low-) waisted” in the caps, should it be aligned with the waist?
5. Where ascenders overshoot cap height, which should it be (vertically) centred on?
6. Where ascenders overshoot cap height, would it make sense to (vertically) align it with the ascender, and provide a “case” alternate aligned to the caps?