I can :)
To actually tell how big it is tho you have to know if he is wearing boxers or briefs/underwear. Bulges in boxers hand down to the left or the right down the leg of the pant, while bulges in tighter brief is usually concentrated to the center of the crouch area. So with boxers I think its easier to tell how big a guy is, usually if he is over 4 inches soft then he will show a slight bulge if you really pay attention, and if he is over 5 inches soft it will be much easier to notice. Usally if he is less than 4 soft its pretty hard to see.