wilbur
>This happened to me once. I sawed the dowels in half and made a thin wedge to fit between the halves, so I wound up with wedged doweled M/T joints.

What I have done since then was make drawbored M/T joints. Offset the holes in the tenon and the mortise by a little bit so that the peg draws the joint tight, so that a loose fit really can't happen.