Thanks, Cecioboe. I missed seeing your post before I posted the one from Dusty myself, ha, ha! Our minds must have been thinking alike that day. Apparently, you could use the string buttons all the way down into the 5th octave of a pedal harp, as long as the strings would fit through the holes. 2MM is pretty large for a string. The lowest gut string, 5th octave A is around 2.30 MM in gut. Since Dusty uses inches and MM, one has to be very careful about the gauges.
Have a great day,
Balfour