First, Mark; there was some discussion on the play spec some time ago. I ‘think’ the opinion was that the actual spec is 0.001 - 003". Some verification is called for?
Apart from that, your logic and calculations seems OK; the master spacers 0.15" is deliberately too thick, giving excessive play - so the thinner the shim the lesser your play.
Whether grinding shims is the right way to go about it; if you have an available supplier - getting the right one seems a better idea?
However; the shim is there only to avoid the nut from squeezing the inner race too close - it’s not a sophisticated piece of kit. In addition to proper measuring tool for the shim - you also have the back-up of play trial and error…
xj6 85 Sov Europe (UK/NZ)