@lewm Actually, the Foz works really pretty well, iff you make sure the test record sits perfectly flat. I had Acoustic Sounds send me a replacement of their test record – used for the Foz – that was dish warped, but I also use both a 750 gr record weight and a 1500 gr outer limit ring to eliminate all possibility of dish warp. It's key to make sure the test record for the Foz is dead flat. I use them both for normal record playback too, to ensure records sit flat. Dish warps are inconsequential.
I have followed that up with a visual gauge and it seems spot on to me. I cannot use that for my 2nd tonearm though, which has a mono cartridge. The Foz is useless for that.