The curves for TXP aren't showing it reaching D-max so, no to that part at least.

TMY can hold about 14 stops on the straight line IIRC, so if you had used TMY instead of HP5 for the shots that started this thread you could have exposed another three stops (7 stops up total) before you even got to the shoulder let alone finding D-max. So again no, the generalization doesn't work.