Lol you make it sound like I alone made it drift off topic
I dont have a tormach yet... Looking at the 770 these days.
I think your best bet is going to be superglue hold down, and a finish pass, you can do a pretty heavy rough pass and leave .005-.010 on the bottom of the slot, and plunge your finish pass into the sacrificial board, might end up faster than trying to get a decent finish in one operation with shallow cuts.
I like to pocket the sac. board to fit the stock so I know exactly where the edges and bottom are without touching off, and I know the stock is flat to the machine.
I use corian scraps for sac boards, with threaded brass inserts in a corian tooling plate to bolt them down. Sure beats mdf, and its free if you know where to look.
Dylan