Scott,
The Hartly was a great boat! I'll have to dig around in the old photos to see if I can find some pictures of it. I'm sure I have some. After my experience with it and how the Belhaven appears to me, I would say you have the better deal as far as construction goes.
The Hartly was a standard sloop design and sailed quite well. One of the things I enjoyed most in the Stuart, Florida area was the ability to pull the centerboard and rudder up and sail out on the sand flats near the inlet. I could sail quite well in 8 to 10 inches of water with just a little board out. It was a great way to get to the good clams! A fair amount of leeway, but managable. With the board down, she pointed quite well and was well balanced. I am being converted to the cat ketch concept and think you will have the better sailing boat when it is complete. Much easier set up at the boat ramp, too.
Alas, I had to move 50 miles away from the good sailing water to a job that took too much of my time and ended up donating the boat to the Chapman School of Sailing in Stuart. I don't know what its ultimate fate was.
I am getting the final shapes on the bottom and side pieces for the Spindrift and am preparing to cut out the bulkheads and doublers this weekend. I am hoping to be ready to "go 3D" either this weeekend or next. Pictures will be forthcoming when I have something worthwhile to show.