It seems like there is a 31 charater limit to zone names, regardless of the Zone Stamp you are using. Is that true? Is there a way to modify (increase) that? If so, where?
No, that is only true for the standard input fields in the zone settings dialog and in the info palette. It seems that both locations do not allow more.
But if you make a new entry in the User Interface, you have no problems to fill in more than 31 characters. Good luck.
Show Data Structure reports Zone name is a 255 character field.
A tangentially related topic that came up recently in tech support email concerned the 31 character Zone Number, which can take "dotted" segmentation. So a Zone number could be "A1234567.8901234.567890.1234567" and via SQL you can query for values in the separate fields named NUMBER_SPLIT1, NUMBER_SPLIT2, NUMBER_SPLIT3, NUMBER_SPLIT4, in addition to NUMBER, which is the entire string between the quotes. So the value in NUMBER_SPLIT1 in the example would be "A1234567". I suppose this might be useful for some sort of space coding. The SPLITs do not have to be approximately equal in length as might be suggested by the example. NUMBER and each of the SPLITs are 255 character fields - although you may not be able to use that many through the AC interface.