That's great Jack! and glad you also had a chance to try the lower tunings....
Please make note, specifically that
the problem with tuning UP, and then DOWN more than 2 semitones, is that once you tune UP, the strings are basically ruined
for down-tuning once they stretch enough, even if they are only on the instrument and tuned higher, for as little as 24 hours...
...the elasticity does not return to the factory-fresh level of string tension, and while it 'might' sound ok in 1st position chords, (IMHO and after testing over 100 different sets of strings) once you tune UP, and then DOWN more than 2 semitones, your
intonation is basically shot, and sharp about 10 cents after the 2nd fret, and that's all up the neck....
I play all the way to the 15th fret on some songs, and have seen the
intonation destroyed by lack of string tension from going UP and then DOWN. Basically if you dont want to have to throw the strings out, you have to tune back UP to within 2 semitones of whatever what the highest pitch.
Maybe if you remove the strings and place them in a bowl of ice water for a few hours they might contract enough to be usable again, but I have not tried this. YMMV.
Martin uke strings are available EVERYWHERE, but the EJ99's are sold at a reasonable price by only a few vendors that I've seen, like on juststrings.com ($7) and stringsbymail.com ($8) - some other sites have them, but at $12/set plus shipping of like $6 - I find that to be pretty steep.
At $12+ per set, you are better off getting some Worths, or Oasis which are double-sets in one string pack.