Love that Karol harp guitar, and that's some fine playing
I don't have one yet, but I'm working toward building one for myself. Just finished up a harp ukulele that is quite enjoyable. I think I'll do maybe one more regular steel string acoustic, and then the full size harp guitar. Depends on when I can get more shop space, since it would be quite a challenge to make something that large in my current nook.
Here's a sound clip and picture of my harp uke
http://deku.rydia.net/music/marmoset_improv2.mp3