I just bought the Porter Cable 2412 Dovetail jig to do blind dovetails for a bunch of drawers for a vanity.   I’m sure I am missing something simple.  Here’s the problem: the drawer back is 1/2″ shorter than the sides, so that I can put bottom mounted slides on.  When I cut the dovetails for the left side – no problem, the top of both pieces are up against the gauge (set after I center the drawer side) at the correct placement (i.e., the top edge of the drawer bottom is over to the left past the top edge of the drawer side.  This results in the top of both pieces being even.  Problem is that when I go to do the other side of the back by flipping the piece around, the top of both pieces is now not against the gauge – i.e., the bottom of both pieces are against the gauge.  This doesn’t work because the bottom of the back is not flush with the bottom of the right side.  Any ideas?  I have tried taking a block equal to the 1/2″ difference and putting it against the gauge and the back and between the gauge and the bottom.  Didn’t work. 

I am also going to try posting this on the Knots forum.  Thanks in advance for any advice