The boat is (or was) located in Friday Harbor WA, the pics are from there too. I spotted it a couple of years ago and got the owners number from the harbormaster, he called back and we spoke for awhile on that weekend. It wasn't for sale then but he would have happily shown it to me except he wasn't close enough to make it happen. So I've only seen the exterior, but he did describe the interior mods - combining the guest and master heads, combining the guest stateroom and master with a new entry via the master cabin. No changes if I recall to the running gear/engines. Having started out as a 58 YF the running gear was already extended from the 53 and no further extension done, I did not ask him how it handled with the extended cockpit.
The lines are very nice. The workmanship was first class, the aft cockpit was perfect. The flybridge was moved forward and the radar arch is one of the few I think fit the YF due the extension. Lots of little up grades like Glendinning cable tenders and control stations coming out of recessed stowage in the side of the pilot house. As he described the mods "he threw way too much $$$ at the project" without any regrets knowing it was all money never recovered. My only negative first take was too much stark white, needed a boot stripe and I prefer Hatteras off white...
I was impressed but left wondering about handling, and value for resale. Now I know the asking price so we'll see how the market treats him. Good luck with the sale and I hope it turns out for him, its cool to see what someone with an open budget did with my favorite Hatteras design.