So I've measured (only approximately unfortunately, got no equipment for precise) the cutouts on BlueNalgene's plate with AEKII layout (I've got not actual AEKII plate, sorry). So, it looks like the numbers you've got are good. Please disregard the one for 2.75u from the CAD file I wrote about earlier, it's way too big (I'm happy I've caught this now and not when the plate is cut).
So the actual measurement I got for 2.75u stab is 21.75mm - and that should be the one I've
linked to before. So a bit shorter than that should be good.
The 2.25u and 2u keys have the same stab distances; also confirmed by looking at the keycaps from the bottom side.
One more I'd like to add is the stab for 6.5u spacebar (AEKII-size), that one is 45.3mm.
PS: Thanks again! Just last weekend I've done
this one manually. I'll compare with the result from your tool - and I'm sure discover a couple more problems with my manual plate