I wear suspenders (formally and casually) and can sort of give you my opinions and insights into them. Keep in mind that my fashion sense is a bit more 1890s than 1950s or modern day. Formally I wear dress pants with button-in Y back suspenders (black) under a vest or jacket. Wearing the same pair casually I may wear them off the shoulders, or over a dress shirt. I always sew my buttons into the inside of my waistband, never the outside. Necessity required I buy another pair recently, and I decided to go for some gray clip-on X back. I wore them casually under a T-shirt -- which I don't recommend, if you're anything but flat they will accentuate the difference between your chest and stomach. I also wore them more formally under a vest. I saw a guy wearing clip-on X backs with just a dress shirt, and he looked perfectly fine for the event. While I prefer the Y back, I mostly see men wearing X backs. I would tend to think an H back would be a big no-no.
