Brad's Jockey underwear is referred to as a "Y-front" and features a "full rise", which was most popular in the 50's and 60's and already waning out of style in the early 70's. While the Y-front is still manufactured it's hard to find anything beyond a mid-rise today.
As with all knit-wear there is a bit of distortion in the garments dimensions while being worn; places where it's intended to stretch more than others. With that consideration, the leg of the inverted Y is nearly equal, but perhaps slightly shorter than the side seam.Barry Bostwick is nearly 6'4", so the waistband would probably come all the way up to the naval on most men of average height.
The length of the center front (when worn) from the center of the waist down to the bottom of his *ahem*, is roughly the same span as the width of his waist.... creating a very "square" effect.
