When I bought Kristy (SM243) she had no sails.  I got talked into a 135genoa of dacron with spectra reinforcement, sorry I don't know the weight.  This sail works with the 155 that came with the boat as a double head sail rig.  However, in light air I would like to have the 155, and there's more often light air than too much air.
I also have a 110 Yankee cut genoa that I use when winds are expected to be consistently above 15-20 kts.  It's a great sail for those conditions.  It's made of the same dacron/spectra material as the 135.

Get the 155, and add a 110...you won't regret it.

Kent