Thanks for the reply.
So I assume you mean measure A on this picture:
For people reading: A is the actual extra stack the top cap will result in. Measure B is the total height of the top cap, which is irrelevant if it is made to fit, since the difference between A and B (i.e. B minus A) is already taken up by the bearing sticking up from the head tube.
The problem with the VeloFlyte one is that the fit is bad on the P5, so while measure A is very small (<1mm) measure B is something like 4mm (IIRC) so on the P5 you have to add spacers underneath in order for it not to hit the head tube bringing your total stack back up to almost the same level as a more standard low top cap.
It seems like the Cobb one is 5mm in total height (but I might be wrong), which would mean it would be somewhat less than 4.3mm in stack height. Unfortunately no specs are supplied so who knows which bikes or headsets it fits…