Iris modifications continue! I found myself needing to reach too often for common combinations with my original thumb cluster of:
space | cmd | fn/mo(1)
I swapped around a bit to make for fn+ combos easier with
space | fn/mo(1) | cmd
The mental stretch of adjusting to new modifier locations is lots lower than that of reaching for awkward chords, so this already feels like a nice improvement.
I experimented with moving the space key to the middle of the cluster, but that made it a little too easy to make errors looking for alpha keys on that bottom row. So far, several common keys I use via that fn/mod key are already feeling much better!