Cool, yes I intend to do it again next month. I’ll also try to apply the same principles on my other instruments. I think it would be a good navigation practice to try to get the same sounds and feeling on for example guitar.
Excellent, I’d love to hear how that is for you. The popMatics stuff is very much geared up for piano keyboard, with the key/tonal centre chosen to make it easier for first-timers to navigate the keyboard (ie using Gb and mainly black keys for the scale) but I’m sure we can find equivalents on other instruments.
It seems likely @mem. With an isomorphic instrument (e.g. P4 guitar) all keys are equal - given enough frets & strings in the direction you want to go! 
On Chapman Stick I’ve taken yet another step away from the usual ‘reciprocal’ tunings (i.e. bass in descending 5ths/,melody in ascending 4ths). I’m still using the same strings as when I mentioned that I’d moved to a 'mirrored 4ths 'tuning (i.e. bass in descending 4ths/,melody in ascending 4ths), but I’ve swapped sides (known as playing ‘uncrossed’) and both sets now use ascending 4ths (i.e. melody in ascending 4ths/bass in ascending 4ths).
On a 12 string it’s a bit like having a 6 string bass for the left hand and a (lower tuned) long scale P4 guitar for the right hand.
C#2F#2B2 E3 A3 D4 B0 E1 A1 D2 G2 C3
I’m still working on refining the action on the bass side.
Yes, the challenge is geared towards learning to orientate yourself on the piano. So starting off with easy to find black keys makes sense. But getting the sounds and relationships in you head/ear you are encouraged to try to find the same feelings in different locations/keys. Will be a challenge, when I’m ready.
What’s your reasons for changing things up? Is it ease of navigation, easier to find/reach notes and/or intervals?
It’s a bit like choosing P4 over standard guitar tuning, but with more ‘dimensions’ available to consider.
I’m looking for the tuning & arrangement that I feel at home with. I was much happier with the 4ths on both sides that Mirrored gave me compared to 5ths plus 4ths. I’m even happier with the layout (physical & mental) that parallel gives me compared to mirrored.
Some people feel that mirrored suits them better since the hands are effectively mirrored too (so same, but mirrored, ‘hand shapes’ for same combinations of notes), but I seem to be happier with the parallel.
To an extent I think some of the choices may depend on what you wish to play, i.e. some chord shapes may be more comfortable with mirrored bass, but bass lines seem to fit more comfortably with parallel?
And of course we all have different hands too!
Thats interesting, I’ve settled on a tuning gor my tenor guitar of GDAD, which I find fits under my fingers and suits the type of music I like to play, mainly the keys of D, G and A. I an get ice ringing string sounds or can get closed chord shapes easily.
@mem I figure that we hope to spend a lot of time with these instruments so if adjustability is available we might as well use it to tailor the instrument to what suits. 
@mem A thing that came up in the IFR Jazz Study Group made me realise I’d missed out on mentioning the word ‘ergonomics’ in my ‘Why uncrossed parallel 4ths’ post, though I did write “And of course we all have different hands too!”
The uncrossed parallel 4ths arrangement literally provides a better combination of angles and thus seems better suited to my body/arms/hands/fingers, as well as to my mental images, so win win. 