I am planning to laminate 2 6mm pieces of Baltic Birch plywood together on a rocker table. I want to net 1” of continuous rocker. I would like to know from some of the plywood builders out there if they have experienced loss of rocker or spring back after gluing. If so, any advice on overcompensating during glue up.
Thanks, Steve

Naturally, you will get a spring back. I use 2,5 mm ply and it gets spring back, but after bonding the top core layer and laminating it, it holds almost correct shape. I am not so sure about 6mm ply.

If you are doing only ply board- from 2 layers, you should make the rocker about 30% bigger because of the spring back.

I would agree with zob.
Wood usually springs back about 25-30%.
Sometimes a little more.
Make sure you leave the board on the table (or clamped, weighted, whatever) for a long time so the glue is fully hardened, especially if you use epoxy, and in cooler weather.....
With epoxy, even though it seems hard after 8 hours, boards can lose their rocker if taken off the table early. I try to leave laminated boards on for >24hours, 48h if I have the patience....