Hey Dan, I didn't noticed you posted, till now.
I am still in the works of the first stage but almooost done. I have Hope Mono Mini post mount caliper with 183mm Hope rotors, I shaped a flat plate of stainless steel to mate the Fournales ISO to a +20 post to IS adaptor. This keeps easily keeps the caliper lined up with rotor. Seems like the simpliest, strongest solution. I will get pics up when I try my new Colbalt drill bits to punch some holes in this stainless steel.
As for stage 2, after shape, hole alignment and all other measurements are true, I am looking a creating the simple flat plate with a bend to rid of the post to IS adaptor. This will be a one piece adaptor, like the A2Z AD-PMR, in shape.
Stage 3, I take to a machine shop using billet aluminum to lighten this design. Of coarse it will be thicker but needed measurements will all be set.
Lots of work but I dare not risk grinding down the Fournales adaptor. Talk soon.