Probably 1/3 of the guys I train with wear a t-shirt under their gi, but one of the guys (sort of a beginner, green belt/intermediate white belt) mentioned that it's actually better not to wear the t-shirt or your sides can get all caloused. Has anyone found this to be true? There is only one guy (just started a few weeks ago) that wears a tight-fitting rash guard shirt, but nobody else bothers. Has anyone found that those shirts actually help? And if I'm only training 3 days a week, for about 2 hrs each time, should I even worry about it?