It's my opinion that simply saying "they don't work" isn't helpful to a conversation about main cap girdles.
In other applications, you betcha they do.
So if they don't/can't work in a SBM... I'd be interested to know why.
Is there something about a SBM that makes them incompatible with an effective main cap girdle?
Or is it simply that an effective bespoke main cap girdle *could* be made.. but never has been?