smart shape button properties

No, I'm sorry, this is a legacy bug, because in versions before 8 shape buttons had only two states: the normal and the pressed state which was a shrinked version of the normal state. This is still the case, and moreover if you are in CP9, shape buttons reverted back to that situation: they will not show the 3 InBuilt states (Normal, Rollover and Down) which work well on normal slides, but they have the old 2-state style. This was not the case in CP8. Please help pushing this to a better position on the Priority list by logging a bug report. Only when enough users do report that kind of bug, will it be fixed soon.

Since position and size of Down state is locked to the same properties as the Normal state, you cannot make the Down state bigger to avoid the shrinking. But I have a tweak (some call me the Workaround Queen): you can change the stroke width: use the Rulers and Guides and make the stroke width bigger than in the Normal state and the shape button will not show the 'shrinking'.

There is no in-built option to turn off the down state effect. You might be able to hack something by getting into the published content but that's for people far more dedicated than I.