<snip> Is it to much or not enough halyard tension? How do you ensure the roller furler works properly?
Usually has nothing to do with halyard tension.
The typical 'problem' is called halyard lead angle ... the angle that the halyard makes between the mast sheave and the furler's top swivel; the lesser the angle the more potential that the halyard will 'wrap' around the top swivel and cause the binding. Every furler manufacturer specifies a halyard to furler LEAD ANGLE and if this lead angle is not met, then you can experience 'binding' of the furler. One solution is to mount a secondary 'lead angle diverter block' to the front of the mast to attain the proper lead angle. Here's another way to do this:
1. Disconnect tack of the sail from the bottom furler swivel
2. Raise the sail all the way up the foil (without binding or jamming the halyard in the mast head sheave .... do this 'softly').
3. Measure the distance between the tack shackle on the furler drum and the tack of the sail (sail fully raised on the foil).
4. subtract 1-1/2" from the distance measured in #3
5. Make up a rope 'pendent' precisely to the dimension of #3 minus 1-1/2"
6. Place the rope pendent between either the tack of the sail and the furler drum or between the head of the sail and the top swivel.
7. With the pendent installed, the top swivel will now be within 1-1/2" of the TOP of the furler foil and the 'halyard lead angle' will now be at its 'maximum'.
If the top swivel is 'noticeably' lower than the VERY top of the furler foil, binding is always a possibility. The solution is to install a 'rope pendant' so that top swivel is at very near the VERY top of the furler foil.
hope this helps.