As someone who was "above average" =P in a past life, I can tell you that CK boxer briefs are the way to go. Ironically, my issue was not wanting to be known for that when I was younger, so tucking it back to the point of screwing yourself seemed to be a help for me when I was still physically a "guy".
It also helped me come off as a scrawny geek and not a porn star to people who didn't really know me =P
If you do NOT want to tuck, you will look like you are at what most people think is erect when flaccid...and take it from me, that really sucks. =(
(On a side note, thank god for atrophy ^_^ I can tuck to the point of NO bulge now, and soon I won't have to deal with that little problem =D)