My Pa-kua uniform consists of black baggy pants with a elastic waist and a draw string, and a white wrap jacket with ties on either side to keep it closed, and the belt. The tops are cut for men, so they wrap fairly low in the best of circumstances and mine is very large because of the way I'm built. Or was built when I got the uniform. This means it opens a bit.
Normally, I wear something underneath - a t-shirt, with or without sleeves, or a yoga top (a sleeveless top with a very high neckline and a built-in sportsbra). Other women might safety pin the top closed or even sew on an extra tie. I like my undershirts. Less fussy. (And if they do decide to tailor tops for women, I think many would be happy. The uniforms are perfectly functional as they are, but a higher wrap would be nice.)
But this time, I forgot. And the top I wore was not suitable for exercising in. So, I had to do the class with just my sports bra under my gi. I kept adjusting things. I mean, I suppose the sports bra counts as modest in other place, but it shows too much skin for my comfort. And there I was with a couple of teenage boys and a male master.
I survived, and I will remember for next time, but it was unpleasant.