formal evening dress: vest or no?

[MacMillan of Rathdown]

That sounds about right to me. The only thing I would mention is over here military Dining in nights are usualy black tie events and are very strict in what is acceptable and not acceptable atire and behaviour wise.

My comments only apply to civilian attire-- those in the military are bound to follow regulations and the traditions of the service.

Im presuming you mean PC or other such jackets here but What about a Sherifmuir jacket? Would that still be a white waistcoat or the usual one?

The waistcoat most often worn with a Sheriffmuir buttons almost to the throat, and is largely covered by the jabot typically worn with that style of jacket. For white tie the traditional black Sheriffmuir waistcoat is acceptable, although I would advocate wearing a white brocade waistcoat with this level of formal attire.

And how about a Montrose which doesn't open?

Jordan

Since it doesn't open, no one will know that you are wearing a tee-shirt, instead of a waistcoat, under the jacket.