try the 3 row button hole.. its similar but makes a bigger hole
--either side of buttonhole, work in established pattern --and for the rows before and after the YO, do the same.--
r1- (at the position for buttonhole) make a double YO (2 yarn wraps round needle), and K2tog
r2- knit (or purl) into 1 yarn over, let other YO drop (it looks a mess, but don't worry!) (finish row in pattern)
R3- when you reach the "YO' from previous row, KNIT INTO BUTTONHOLE, not stitch, (and let the stitch drop off needle as if you had knit into it)
it still looks a bit messy, but trust me, its ok.
(R4--work row in pattern (garter, ribbing, what ever) look at buttonhole again.. Amazing! no longer a mess, but a nice neat buttonhole, not a big one, but twice the size of a Yo/k2tog style one! and not really much harder!
for other great buttonholes check out Lucy Neatby's web page, trade winds, and find the bosun's chest--free tutorials and ideas there, including some of the best knit buttonholes i have ever seen!