As I have said many times, the optional jib simply does not work in light air, moderate air, heavy air, or any kind of air. The reason is you cannot get enough tension on the jib luff.
The tack of the jib is attached to the crossbar between the bows. The cross bar does prevent the bows from toeing in, but when you try to exert enough pressure on the halyard to tension the jib luff, the crossbar will simply bend, and if enough tension is applied, it will break.
If you are going to have a jib, you must use the crossbar and then have very low bridle wires strung so the tack location is very close to the crossbar. Then you can exert a lot of luff tension and it should work.
However, the sail is very small and will not gratify you much, I feel certain.
If you want some speed, get a Hooter.
http://store.catsailor.com/tek9.asp?pg=products&specific=jmnrkomnk0
They work. And despite the large size of the Hooter, you can sail upwind as close as other Waves sailing unirig.., and much, much faster.
After the wind gets much over 12mph, however, you will have trouble holding it down. Next move is to rig a trapeze.
Check out the article on Hooters and all the links within the article at http://www.catsailor.com/update_hooter.html
Good luck,
Rick