I had a gooseneck system like that on my first boat, a folkboat
type with a masthead rig. I ended up fixing the boom in position, much better for slab reefing. With modern winches, sails
and spectra halyards the halyard tension can be set up tight enough and there is not the same need to tension it down from the boom end. A cunningham is much easier to use if you want to tweak the luff tension.
IIRC those sliding systems for roller booms were handy in that you could drop the whole boom a foot or so and then make the halyard fast. Then you could wind
it up with the roller reefing boom.