From the picture you posted, it not only looks thick, but even fluffy on the inside. It definitely has some bulk. I suggest it, and probably just wear a thinner shirt underneath.Interfacing is like the stuff you iron into the inside of fabric to make it stiffer/stronger and add more body to it
its used on things like the inside of purses and aprons .
Im a bit concerned with it not being breathable, the vest is going to be over another shirt so I don't want to get too hot wearing it in the summer and stuff
and im also worried that it might look too stiff,
If I just picked out some thick fabric, I feel like it would be stiff enough, but I was wondering if anyone had experience making vests with interfacing, if adding it would be a good call or not.