Hi Rob,
Use the #6 SLX on the #6 rod, you'll find it easier in a coastal breeze and to make sure that the fly gets to where you want it first time.
Do a google for Lee Cummings website, STS flyfishing, there is a fly on there that will work. Other flies will depend upon what the food source is in the area you are fishing.
Be interested to see how you get on.
Cheers
Ben