"Guitarron" means "large guitar" in Spanish. One way to determine whether or not to embark on the task of building a stringed instrument is to assemble a kit professionally prepared by a luthier. However, in the case of the guitarron, there are no ready-to-make kits (at this time). Designs and blueprints may be available through luthiers who specialize in Latin American instruments. I found a luthier named Javier Rivera who is based in Mexico. His advertising on a Spanish language website offers several instruments including the guitarron: "PARA CONSTRUIRLOS UTILIZAMOS PLANTILLA MORALES" [translation: We use the Morales Template to construct them]) You can find Javier's information by entering the following url: tlahuack.olx.com.mx/vendo-vihuelas-y-guitarrones-finos-para-profesionales-pantilla-morales-solo-conocedores-iid-44212605. Otherwise, to make a guitarron, you should do what Ken Cartwright of Cartwrights Music Repair, in Stayton, Oregon said during a visit in February. "Buy an affordable guitarron and take it apart. After you put it back together you will know how to build a guitarron".
Cheers!