At your weight, in the conditions I've experienced in your area, I would make the 6.5 m2 your small
sail and add something areound 7.5 m2.
Ultimately, I'm pretty sure you will need an 8.5 m2 or larger to suit the sometimes light wind conditions
in your area.
I'd suggest a 7.0-7.5 on the Rio L first.
You have the basic skills, so a really small rig isn't going to be needed.