I went looking and found the Cosmos tool for customizing a Dactyl Manuform, that's what convinced me to make one.

https://ryanis.cool/cosmos/beta#cm

I was able to measure my finger bone lengths and customize the keyboard to match. Very cool stuff!

No, but I've been typing on one for five years anyway.

The concave keywell shape of the Dactyl Manuform is more ergonomic for me than flat keyboards, even when they are tented with an opening angle. (I had a two-piece flat keyboard, the Keebio Fourier, before this Dactyl Manuform.) I expect it to be more ergonomic for anyone.

The thumb area of the Dactyl Manuform is constructed with the idea that you will actuate the keys there using the pad of your thumb, not the side. The original Dactyl and the Kinesis Advantage 2 have a thumb cluster which is raised up relative to that of the Dactyl Manuform, and I think this is more correct.

With your HHKB and Realforce collection, you might be interested in the Dometyl, a keywell keyboard made to support capacitive rubber domes. Its three thumb keys are probably angled better; but I have not yet finished building my Splaytyl (another variant in the same repository).

I've got a bastard Scylla and it's a dactyl manuform + ergo, but.. I have to say thumb cluster and reaching is a little much sometimes.. Maybe I have to do less ctrl+ tilda for my clipboard selection..

Well is it? I have heard its got the best layout in terms of ergonomics and can be customized a bit with layout and hotswap. I also own several HHKBs and Realforces. So I'm interested in how they compare.