From your video at 4:45,
hmmm,, hey, why not use the bottom four strings for G2 C3 E3 A3, a full octave lower than a low G tenor tuning.
Yep, that’s an octave ‘ukulele. Guadalupe makes a set of strings for this purpose, and you can purchase them from Mainland. These are all wound strings. Several threads have explored various other string sets which can also accomplish this.