edsobo

Ah, I see. That makes more sense now. Thanks!

Is it completely necessary to shim the board so the whole surface is lifted off of the backing? It seems like if you left part of it touching the support and shimmed the high spots, it would be less likely to flex during planing.

As I recall, it was mostly a trick for gluing the magnets in the right spots. If you put them on a lid, you can position them and then put the glue on the other side and when you stick the other lid on, they'll still be in the right spot since the second lid is the same shape as the first. Without the double lid arrangement, the magnets shot out of hand and onto the lid as soon as it got close, which led to unpredictable results.

Sounds like you're talking about the Whitlox forge. I got one a little while back. As soon as I finish getting my anvil stand built, I'll be able to give it a spin.