Not recommended!
The 5.9 is a quite finely balanced two man boat and even with the jib (5.9sq m) it can stall upwind if both sails are not trimmed correctly when overpowered. The 5.2 sq m jib doesn't choke as easily but is still far too much for singlehanding. If you wanted to singlehand one you could maybe try a dart 18 mainsail (I've seen it done on a Tornado) but your not going to get 5.9 performance. It may even work with the self tacking SX jib (about 3.4 sq m I think.) Also make sure you have help around for if it goes over.

By far the easiest solution GET A CREW! they are great boats.

Cheshirecatman