my idea of PRO ( as explained over on simon's gazzetta della bici post 'the PRO life') is a full zip.
this means the jersey or for extra PRO points gilet, gets unzipped at the first hint of a climb and flaps away behind you as you big ring your way up, turning that hummock on your commute into a poor man's zoncolan...

and for more on bigringing, check this blog out. hilarious.