A lot of people seems to have a hard time deciding which Twiddler layout to use.
As someone with thousands of hours of Twiddler use, I decided to share my experiences with Twiddler Configurations.
When I first got Twiddler 2 almost two years ago, I didn't know much about chording and layouts.
So I started using the layout that came with it. I used it for for days.
Then I've read paper "The TabSpace Twiddler Key Assignments" written by Brandon Rhodes in 1999. http://rhodesmill.org/brandon/projects/tabspace-guide.pdf
I was very impressed by it.
Mr. Rhodes identified several shortcomings of a standard layout:
The default assignments provided by HandyKey were deeply dissatisfying because of their staunch disregard for efficiency and
the difficult (at times approaching haphazard) placement of punctuation. The alternative developed by Brad Rhodes(which may
be downloaded from HandyKey’s web site) certainly showed a heightened sense of efficiency, butseemed to lack the strong
spatial associationsthat would make a key mapping easily for me to remember.
He also came up with several principals that allow making Twiddler layout easier to type.
It was very convincing and logical, so I switched to TabSpace layout.
Almost immediately I saw some shortcomings in TabSpace too:
* The most dexterous finger - the index finger - is not moving when letters are typed, but other, less dexterous fingers do move.
This got to have negative effect on the typing speed.
* Assignment of letter chords was not optimal.
For example, "q" is 16 times less frequent than "b", yet "q" uses three middle "home" row buttons and "b" uses one middle row and two side row buttons. Moving fingers away from the home row is not free in terms of the speed.
* Several characters had multiple chords. For example, "." is both RMMO and LLOO.
This seems to me counterproductive from muscle memory point of view. It also wastes valuable chords.
* Several chords are very rare and didn't warrant a chord assignment. For example, "hn", "ho" and "hr".
Maybe they are used in other languages?
* This layout was missing other frequently used chords according to this source: http://practicalcryptography.com/cryptanalysis/letter-frequencies-various-languages/english-letter-frequencies/
* Arrow keys are not easy to use as they involve FN key to press them.
* Copy and Paste keys didn't work on Mac. These are the keys I use the most.
* Other shortcomings were discovered after several months of using TabSpace layout.
I proceeded with gradually improving TabSpace layout.
At first, I tried keeping my modifications to the minimum, leaving the letters without any modifications.
But after about a year of using Twiddler as a replacement of the standard keyboard I decided to leave no sacred cows.
Thus Backspice layout was born. By now, it only has a vague resemblance of TabSpace. Even the letters are not the same now.
This post is becoming pretty long, so I'll leave explanation of Backspice benefits for another time.