You can certainly do either a fixed or moving gooseneck. I've sailed dinghies for a lifetime, and even the professional builders/designers of various popular dinghy class boats don't seem to have ever decided one way or the other.
With the sail being provided (as shown in Captain Skully's picture) he has a consistent grade of sailcloth right down to the foot (as would be expected for a loose-footed sail), but with a fixed tack and cunningham. I'm sure that it all works, but in higher winds you'll be cranking on the cunningham and outhaul to flatted the sail, and - possibly resulting in a fairly big wrinkle and a bit of "flappy" sail along the foot. The picture already shows the beginning of the wrinkle.
Even in dinghies with a fixed foot sail (sail attached along the length of the boom), in an effort to maintain a nice, unwrinkled sail shape as low as possible on the sail, more modern sails are being designed with a panel of softer sailcloth along the foot. With the outhaul and downhaul tight this creates what sailors call a "shelf" in the sail. Sail trimmers will refer to the size/appearance of the shelf when trimming for various with conditions.
I looked at the Passagemaker pictures on the kit sail portion of the website and note that with the aluminum mast they are rigging with a downhaul on the boom and/or to the tack of the sail - no conningham. I'd try to accomplish that on your Passagemaker, even with the wooden mast.
Refering back to Captain Skully's picture above (and of course this is just me) I'd rig the goosneck-to-tack connection like he shows, but substitute for a sliding cart on the boom end of the the gooseck universal that will fit your sail track. The portion of the track going up the mast that takes the sail slides I'd leave alone, with the bottom of the track at about the height shown. I'd leave a gap of about 3-4 inches (just enough to fit the gooseneck slider) then add a second piece of track below, with plenty of excess to provide room to pull the boom down with a downhaul, even on an old, stretched out sail. The length will also increas the number of screws holding this shorter length of track onto the mast. Just not so long that the boom slides down to an annoyingly low height when not rigged with the sail, and not so long that there ins't room for some type of downhaul cleat or whatever below the track. Put a stop at the bottom of the track to support the boom when the sail is lowered.
In rigging, you might develop a system where it is easy to detach the mainsheet from the boom. You then could avoid ever undoing the outhaul and routinely just pick the boom up off of the track and roll the sail around the boom. Or even find a gooseneck with a unversal that allows the boom to spin.
Anyway, my two cents, and as I said, the history of dinghy design proves this issue has never been decided. Not being a race boat, whatever you come up with will be good enough.