Assuming you are attaching the tack of the sail to a pin or a hook on the gooseneck or boom, beyond that most similar setups have a tackle or strop to keep the sliding gooseneck in place against the halyard tension. This allows you to set the gooseneck height, and can act as a cunningham of sorts itself.
Alternatively you could get a couple of track stops that fit your track and locate the gooseneck that way - but it will be less adjustable.(or replace one or two of the track bolts with ones that stand proud - does the same thing more permanently)
I'd probably fix the gooseneck in an appropriate position with stops, and rig a conventional sly pig (cunning ham!?
btw - the Shark was our first sailboat - great starter, but we outgrew it the first year.