You might want to check out the grooming section. I know there have many threads about keeping a top knot in. Appears that many have the same problem you do.

~Joanne~
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Joanne

Eli

Chipper

Eva

Snowboy

Rosie(R.I.P. 1996-July 29, 2013)

Cocoa(R.I.P 1998-April 26, 2012):