Bruko octave guitar/Oktavgitarre

A lovely miniature guitar by the great German ukulele company Bruko, just 60cm long and 20cm wide, with a 36cm scale length - it fits into my concert ukulele's hardshell case, at a push! Its top back and sides are made from solid okoume. When I bought it, second hand, it was fitted with steel strings, which seems to have been what its manufacturers intended, and it was unbelievably loud, with a phenomenally clear chiming ring to it. However, it was virtually unplayable about the 5th fret and very hard work for all but open chords. I tried swapping the metal strings for a Cordoba Mini A guitarlele set but found that the third (third-thinnest) string was too thick for its nut slot. My solution was to move the strings across one place, dispense with the lowest string and use an Aquila Nylgut ukulele A string to fill the gap at the 'treble' end. After a couple of snappages of the Aquila string, I found I could only tune the guitar up to D (D, G, C, F, A, D, from low to high), not quite an octave above standard guitar tuning. This sounded bright but warm and it was possible to play classical guitar pieces and all manner of other guitar music, with a very sweet sound and good volume. I have now replaced the Cordobas and Aquilas with Fisoma Silber nylon strings made for octave guitars - these are the ones heard and seen on the above clip. Again, the third string was a little thick and I had to tamp it into its slot with a table knife. The volume is lower and these strings do not have the clarity and sustain of their predecessors; I wonder whether a set of Savarez SOP 670R NT octave guitar strings would sound better. I suspect Hannabachs would be too thick for some of the nut slots. This is a beautiful instrument but I find it quite tricky to play with the strings so close together on such a short fretboard and a lot of pieces are impossible without adaptation.