I have no experience (yet) with top down furler.
I have a Facnor AFX with a central furling line.
The difference from a top down is that it have a swivel top & bottom and a thin line attached mid luff that is used to furl the sail from the middle.
The sail I'm using has can be used in a wide AWA angle from DDW to 90° by adjusting the stretch on the luff.
The only adaptation for the furler is a reinforced eyelet in mid luff.
It's important that the head and tack can rotate freely during the furling process.
Here I'm sailing DDW with the tack eased, you can see the furler flying, the furler sits on a 1:2 tack line that can be adjusted from the cockpit.
In this picture you can see the central furling line going to the torsion stiff rope.
The tack swivel
Maybe I'm wrong but I think Facnor has patented this design..
I'm planning to convert my system temporarily to a top down just to compare the two different designs - out of curiosity