my first 742 case rebuild, need alittle advice please

Ok so here is where I am at, I put it all together set my back lash and checked my pattern, unfortunately it is high on the drive side and low on the coast side, so according to my pattern comparison in the manual I should remove some pinion shim, so I took it apart, ( even managed to get off the pinion bearing with out damaging it ) I figure I would take out 15 thou of shim as I started with 90 thou as recommended then I put it back together the drive side seems better maybe a bit high and the coast side is still too low so I guess it comes apart to remove more shim, any ideas how much to take out? I was thinking 20 thou which would take me to about 55 thou but that seems thin?