Thanks for the notes and being willing to share the cleats! I am over here on the Left Coast of the USA, pretty sure shipping would cost more than cleats but definitely appreciate the offer.
The shim was originally installed by a fitter and based on a measured tib/fib leg length difference. 5mm so it is on the bigger side of adjustments but not crazy I think. Have good hip flexibility and am reasonably bendy all around with a medium aggressive fit on the bike. The fitter who set up the shim has a good reputation for the physio side of things. Shim might not be the only solution but has been functional for a couple years outside of the cleat issue.
I have used cleats with different amounts of float, feel like the 4.5* is a good middle ground between feeling loose and zero float. Not sure it has a big impact on my cycling either way but like the feel of higher tension pedals and less float on the cleats. The shim marketed as Keo specific but the holes in the shim match the slots in the cleat, which leaves some open space under the cleat instead of supporting it more fully like the sole of the show would normally do
Figuring out how to support the cleat better around the shim is definitely a good idea, going to mess with that a little bit and see what I can do.