How close is good enough regarding installed height

You could also get offset retainers, i think crane used to do them, not sure if they are still available.

offset lock and retainer will get you there, and leave more space for the "armpit" of the rocker.
the offset retainer sat at the same position on the stem but the rim/ spring contact area, was for want of a better word, lower, basically the centre of the retainer didn't sit lower on the locks the offset was in its rim.... this you avoided a stack up of offsets that caused you to hit the stem seal at full lift which is what would happen if you moved it all physically down the valve stem.