I had an experienced luthier add one soundport on the player side between the neck and shoulder curve to my Cervantes Master. Based on some research and a survey of luthiers, I requested a single 30mm size hole with rounded edges (this is the size now used and suggested to me by Fritz Mueller, the Canadian luthier). A 30mm Forstner bit was used to cut the port.
Results: very pleasing, at least to my ears. I had it done for the player's enhancement rather than any attempt at increasing volume for an audience. The guitar is loud enough as it is, but the added sound coming toward the left side of my head feels as though I've gone from mono to stereo sound. The entire instrument feels like it's vibrating more, so there's a pleasing increase in the tactile senses while holding and playing the instrument. And though I was a little worried about any effect there might be on the tone, the soundport seems in fact to enhance the depth and richness of the tone overall in a subtle, but very distinct way.
I like it. I have a maple/spruce that I'm going to drop off for the same minor surgery.
Has anyone else had this done? I'm wondering what the results were like for others?