what strings do you use to string the box guitar?
You can pretty much string these guitars any way you want, but for a four-string CBG I usually use the 5-4-3-2 strings from a set, if I want to tune to an open chord tuning. I also use the 4-3-2-1 strings and tune it like a regular guitar, which in effect makes a four-stringer into a "tenor" guitar, to be played just like a six-string guitar but without the bottom two or low end strings. For a three-stringer you can use the 5-4-3 or the 4-3-2, or even the 3-2-1 strings. This can be helpful if you want to do open tunings in different keys, as the one set allows for some lower keys while the other can tune to higher keys.