I have a couple of Kirk Sand nylon string electrics. Kirk recommended the D'Addario Pro Arte Composite Core EJ44C, (extra hard tension composite core) but to replace the G with an Alliance Savarez 543-J. I've tried other approaches but always come back to to the EJ44C with the Savarez G. Here's a video example of these strings in action. (Sorry for the distortion on the harmony guitar, the mic was too close to the amp).