The column stagger in ergodox works well with the hand hand positioned at a slight angle, [...] It is basically the same that I do in a non-column staggered keyboard,
The issues I have are (1) the switch axis is not parallel to the direction of finger flexion, (2) even with such a hand placement, the the closer-in pinky keys and the further-away index finger keys get hard to reach and in general the index finger ends up with a flexed proximal joint at the top of a key, making it weaker and less comfortable (luckily the index finger is pretty strong, so this isn’t a complete dealbreaker), (3) flexing the index finger at the second joint lands it on the bottom key of the middle-finger column, etc. [a row-staggered keyboard accommodates this: the fingers go from FDS to CXZ and from JKL to M,. when you flex them], (4) on the Ergodox itself, that puts the thumb keys even further away, when they’re already too far for comfort for small-to-medium hands when the hands are straight (not necessarily a problem if you move the thumb keys).
I'm finding some keys harder to reach with the index and pinky fingers in your design, because the hand starts of as more extended.
The fingers should not start out extended. They should start out in a neutral position, which is a kind of quarter-circle arc shape, with the distal phalanges at a maybe 70–85° angle to the direction of the forearm, depending on your specific body shape and typing style.
the increased middle finger stagger makes a little more awkward to use an inverted T arrow in a FN layer on keys ESDF.
If you want an inverted T (or in this case more like a diamond shape) Use DSCF instead. :-)
Or better, use middle and ring fingers as left/right (or right/left, depending on which hand and your preference), and put up/down on the index finger and thumb, respectively.
At that point I finally realized that I can move the thumb keys anywhere I want (with reason) just by adjusting the stagger!
Something like that, yep. It’s even easier if you can adjust the vertical height of the keys in different columns.
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Your result looks pretty good. If you make a working prototype, let us know how it goes!
I'm not 100% sure if the Tab and F4 keys will be easy to press with the thumb w/o hitting the keys under it,
They’re going to be fine, IF
you make sure to use extra-tall keycaps. Something like SA or “OEM” profile keys when the rest of the caps are DSA/DCS/Cherry profile, or if you can find some, maybe the extra-tall F-row caps from Cherry or DCS profiles.
When over a key switch will I prefer smaller key caps a little higher up to hit with the tip of my thumb?
My preference is to use the side of the whole distal phalanx of the thumb to press the primary thumb keys.
If you ever get the chance, I recommend borrowing a Maltron keyboard for a few days, and trying to understand why they chose their particular position and angle of thumb keys.
A large 1.75u space bar may not be such a good idea with the problem of hitting it off-center
1.75u will be okay without stabilizers (2u really isn’t). I think 1.5u works slightly better though. YMMV.
The Tab key is relatively easy to hit if you float your hand up a bit, but is bad for holding
It will be totally fine as a modifier/shifter if you use an extra-tall keycap.