Optimum knot depth?

Just got done turning my first brush. I have a 20mm Woodcraft badger knot but I'm not sure how deep i should set the knot. As of right now I have around 15mm depth cut into the brush handle. Just hoping someone can point me in the right direction i dont want to find out the hard way that i didn't set the knot deep enough , dry fitting it seems to look ok.I will try to post a pic if it helps any.
Thanks,
Jeff

I set it as deep as it takes to cover any sign of glue or deeper if I want more backbone.

You want to measure the loft,from the upper edge of the handle to the tips of the hair.
As a general rule a face lathering brush will have a loft of about48/50 mm.
A bowl latering brush 55ish,depending on the density of the knot of course.
Bore,fit, measure.