I bought a suit by Intersport many moons ago. As time progressed my gear changed and the suit ended up spending more time hanging in the closet. As I now am down to just the bike as transportation, I pulled it back out, wouldn't you know, it shrunk in the closet, mainly around the middle....... My commute is about 15 minutes, and involves 3 turns, one of which is out of the driveway, most of which is 4 lanes. Recently I've taken to just throwing on my jacket, gloves and helmet, wearing my shorts and work shoes. Not the best gear for riding, but considered the distance/time involved, versus fighting my way in and out of the suit, I'll take my chances. When school starts again I'll probably switch back to full gear, too many kids getting their licenses over the summer...... But I digress......
My intersport was always tight in the butt, always long in the leg, when I switched to the ST the butt area seemed to have more room, probably because of the different sitting position(cruiser to tourer) but the legs seemed longer. Pulling the kidney pads out helped with the middle, still tight, but better. Intersport suits were along the same lines as the Aerostitch, but using two zippers instead of one long one, and having a waist belt to cinch in the middle(which is currently at it's maximum setting)I've never found off the shelf suits that fit me right, and dream of a tailored suit one day. Jackets fit me fine, it's just the stumps I call legs that cause me issues. I remember when my waist was the same measurement as my inseam, I was basically square, now I'm more of a rectangle.
Try pinching in the seat area with clips until it fits where you want it, then sit on the bike, clips that pop off show tight areas, where the clips stay shows where the suit needs to be tighter.