Dave, do you read Spanish? I found some tab sites, it looked like, for the cuarto, but all in Spanish. I also found some sites which said it was an important component of llanero (cowboy) music in Venezuela. I'll ask Rog if he saw any while he was down there. He loved listening to the llaneros and came back with a couple of tapes of their music.

It, evidently, is important to some Puerto Rican music, too, according to this:

"Cuatro - A small, ten-stringed guitar, one of the many guitar variants to be found in Spain and Latin America. The cuatro is a major instrument in Puerto Rican jibaro country music."

Nothing on tunings, though. Good luck!

kat