Thanks, my main concern is that these can be loaded in chains in other headers (esp, considering that this is a data format header)

Still.. 
(... I had to look it up)
http://cmsdoc.cern.ch/cms/cpt/Software/html/General/CodingAndStyleRules.pdf
Sec 3: CMS Coding rules:
15. Dene constants using enum or const, never #dene or magic numbers.

Also, it's a better style to have constants in caps