formal evening dress: vest or no?

[piperdbh]

I don't see why you couldn't wear a 5 button vest with jabot but I'm no expert... I don't think I've seen that look with a PC though... do you have any pictures?

Lace jabot and cuffs is for white-tie events, which are more "formal" than black-tie.
For the PC, I think the low-cut, 3-button waistcoat with bow tie is better. Here's a shot of yours truly: