Adding 2 extra strings (Chikari) to an electric guitar as an adaptation for Hindustani music.
As my first experiment, I chose a $15 Goodwill special (First Act) just to see what the results would offer.
I cut off most of the old headstock at a 15 degree angle and grafted some grain-matched maple in the same way I would on a custom guitar neck. It creates a very strong neck, as the wood grain runs parallel to the headstock (instead of at 15 degree angle) and therefore more resistant to breaks.
I always laminate a veneer on the top, in this case Brazilian Rosewood. This dresses it up, and adds a lot of strength to the joint (not that it needs it):
For the bridge, the fixed-bridge they had on there turned out to have enough room to drill to small holes, spaced just right from the bass string, to run the two chikaris through. All that was left was to make a small bridge (out of steel 1/4" stock) to hold the chikari's about 2 mm above the plane of the melodic strings:
On the nut end, I just created a nut that extends about 3/8" past the bass end, and left it so it could be shaped to hold the strings (again) about 2mm above the plane of the melodic strings (that comes from my friend who plays sarod in the Shah-Jahanpur gharana- they have their chikaris about 2-3mm above the main strings):
I will upload a video someday if I get the time! Contact me if you have any questions on this process.
Note: Cut your guitar up at your own risk!!!
'Crafting a nut' and 'grafting a headstock' are terms I'm using lightly- it took me about 8 years to get my chops up on that stuff building custom instruments, and I wouldn't necessarily recommend for the DIY'er unless you have a lot of experience!