Your best bet is to be carefull and move around shims you have untill you have all the clearances that you can get right done, You can always grind them down a bit if too thick and clearance is tight.
then measure the ones you need and go to mr subaru, think they go up in 0.1or 0.01 increases.
Also make sure when measuring that the bucket is actually sitting on the shim and not the retainer, if shim has been machined in past its possible to move it to different valve and even do its measuring correct the shim is too thin and bucket is on retainer