I have found that I get better results when I use a tennon instead of a
recess - the chuck can get a bettr bit in the compression mode versus the
expansion mode - you may want to try using a tennon and then jam chucking
the bowl to finish the bottom

With my Nova chuck (although the original author has a compact version), I
get MUCH better grip in expansion vs. compression. Don't get me wrong, the
compression is great, but in expansion, I get more solid holding with less
visible marring of the wood.

I rarely, if ever, make the recess (or a tenon, for that matter) the full
depth of the jaw's dovetail. I just make sure that the angle of the
recess/tenon is such that the farthest point of the dovetail is what makes
contact first, and then things go great. Good enough, in fact, that a year
or so ago when I first tried purpleheart and made a rather stupid mistake, I
broke the tenon off of the piece before the grip of the chuck gave up.

steve