Offsetting Domino depth

Currently, I'm waiting for the new 4mm Dominos and cutter to arrive at a local store. These would solve my problem immediately.

But, no need to wait.

I need to put Dominos into 12mm ply sides and into 1/2" wide oak "banding" that will form a flat sideless drawer for my shop (all my drawers are like this in the shop and I find them too useful).

Problem: 5mm Dominos will fit into the 12mm ply, but the minimum depth of cut is 12mm, which is 1/2mm shy of punching through the banding. Just say 'no' to punching through.

My solution is likely inspired by those narrow stock spacers I discussed earlier. That is, I took 2 rare earth magnets that were 2.5mm thick and stuck them on the end of each registration pin. Now I can mortise on the 12mm depth and get basically 9.5mm deep mortises. I won't punch through. That leaves 20.5mm of the 5mm Domino to go into the ply, which I prefer anyway, so I can set the depth of those cuts to 20; the Domino really isn't 30mm; it's shy of that and everything works great.

Naturally, use strong magnets for this to make sure they stay put. I didn't have any problems. A non-magnetic version of this trick is to rip a small piece of wood 2mm thick and carpet-tape it to the face around the pins.