no doubt your ported channel idea allows for greater piston shimming (stuffing). Tolerances will probably vary, but with the conventional approach, my best effort was with a .025" shim and an o-ring change to U90D 117 (this is a little larger, oem is metric iirc):
I never had much luck with foil tape as a shim. I think that the pressure, combined with the lube and moisture condensate, had their toll with the adhesion. But, it's great for testing...easy on, easy off. Well done!