Second try with a (maybe) more practical layout :

Second try with a (maybe) more practical layout :
- layer modifiers in the thumb clusters, Alt-F1 - Alt-F4 should now be easier to type
- new Alt and Ctrl keys in the bottom row are more easily reachable with thumbs than the little thumb cluster keys, and feel more like traditional keyboards
- thumb backspace wasn't great due to lower precision and repeat rate than index fingers