I have bought several sort of old traditional gueuze among other 3Fonteinen and Boon Mariage Parfait, there is as good as no pressure in the 3Fonteinen bottle, which you don't have with Boon's gueuze (where you must be some carefull at opening it).
I thought that gueuze needed a champaign bottle because of the pressure. But definitely not true for 3Fonteinen... or do we all handle those bottles badly?