I have at least some background information on these guitars already. I have been to, I think, most of the "usual suspects" websites. There are devotees out there, some people have 10 Daions! But someone here may know.

What is the difference between a Daion and Mugen? They look identical, as far as I can see (inside and out) and they seem to have identical model numbers.

I used to have just one - a THE78 Heritage. NOw I have two, the new one being a THE78/12 Heritage. Slotted head, very pretty.

But the previous owner (had her from new, but obviously never read the manufacturer's instructions) had always used 13s on her from when she was new in 1982. Some "relaxing" of the neck and top are going to be needed, and probably a Bridge DOctor, but with luck a neck set can be avoided....