This is something we all perpetrate at some point and it is in such instances that we learn lessons regarding style and execution. Today's topic is very short but important; should you wear a tie bar with a waistcoat. And the answer is a resounding no! There's absolutely no need. The waistcoat is already fulfilling the function of a tie bar by holding the necktie in place. I wear all my waistcoats with a deep V. I actually have a navy blue waistcoat altered by lowering the button stance because it was too high. I like to show off some of the necktie, shirt, and the relationship between the waistcoat and jacket. If you're stuck with a necktie that moves around while wearing a waistcoat then it means the fit of the waistcoat is incorrect. This can be corrected by using the adjuster belts at the back of the waistcoat to tighten it. This works almost all the time unless the waistcoat needs further altering. For waistcoats that don't have back adjusters, like the one I'm wearing here, you can have it taken in at the sides and the back until you get the perfect fit.
Whatever you do though, don't wear a tie bar with a waistcoat.
PG: Man to man, generation to generation.