Per Aerostich's sizing chart, a 50-S fits best for: 33.5" inseam, 44" waist; 50" chest; 205-250 pounds, and no more than 5'11" tall.
Next size down is 48-S: 33" inseam; 42" waist; 48" chest; 190-245, and 5'10".
Next size larger is 52-S: 34" inseam; 46" waist; 52" chest; 220-260, and 6'.
I have noticed their sizing is small, i.e. if you have a true 42" waist, their 42" waist will be way too snug, and a 44-46 fits much better. Similar for their max height listing, better add an inch or so. In short, better to be a bit too large than too small, unless planning to lose serious weight, or shrink in height.
Just for comparison, I thought I would throw my numbers in. I am 6'2, 280lbs, tall upper body, 54 chest, waist 45" and a 34" pant length. (honestly don't know the true inseam measurement?) My suit is a 54s and stock no adjustments made. There is plenty of extra room for undergarments, and armor. Hope this helps a little? Jon