Well, to make things short, the only time B-C (boys) has instituted a 4-5-1 game plan was when the Bearcats were pretty much decided underdogs entering those matches.
I can think of Northwestern this year (a 3-2 loss at USC's practice fields) in which we ran that formation (actually our variation was more of a 5-4-1 to clog the middle against the Trojans' prolific midfield/forward attack).
I know in 2004 with a nucleus of sophomores at the Carolina Soccer Classic and just one senior and one junior in the lineup that physically we didn't match up that well with host Wando. However, the 4-5-1 in that instance kept the game within reach and unfortunately at 1-0 down with just minutes remaining we missed a back post opportunity. As it goes, the Warriors countered a wide-open field and shoved one into the back of the net to win 2-0.
Generally, Brookland-Cayce has run a 3-5-2 or traditional 4-4-2 the past 6-7 years, while on occasion implementing a 3-4-3 (2002, in particular). Personnel dictates the formations available to your squad.
But, a 4-5-1 (or its variation) does not lend an exciting brand of attacking soccer unless you have quality outside midfielders that are simply more talented than opposing midfielders and backs. Thus, the outside mids can dictate the pace of the match and support the lone forward.
My opinions of course!