You're saying there is no possible way for a player to get 48 minutes in a blowout?
This is correct.
Blowout = Result with at least 20 points difference, is that right?
Well, if you take only 5 players to the match, they'll probably play 48 minutes each (unless they're fouled out or injured, of course)
Heh, I got confused by the topic title, which has something to do with forfeits. There is no way to get 48 minutes in a forfeit.
There is, however, a way to get 48 minutes in a blowout, though it's not 100% guaranteed. What you can do is make sure you have no subs for the players you want to play 48 mins, and no unassigned players in the match list.
"I don't know half of you half as well as I should like; and I like less than half of you half as well as you deserve."