I'm not going to suggest which flex is best for you, but I will give you a bit of advise on what you should consider.
Aside from ability, terrain skied, wt and size the main consideration becomes how does the snow, ski, boot, body interface work.
Snow and body you've defined already. Boot is what you are looking for that leaves ski.
Too stiff a boot and too soft a ski, you'll over drive the ski (skiing will suck)
Too stiff a ski and too soft a boot, you won't be able to drive the ski (skiing will suck).
Balance this and you will enjoy the package you have and the skiing you do.
I've tried to make this intentional short and sweet without giving one recommendation over another (don't worry others will).
My personal preference is on the stiffer side as I ski well enough to moderate input (so over driving is not an issue, usually), what I don't like is providing input and it not being transferred to the ski (too soft a boot). I also like stiffer skis (so stiffer boots are in order).
Aside from ability, terrain skied, wt and size the main consideration becomes how does the snow, ski, boot, body interface work.
Snow and body you've defined already. Boot is what you are looking for that leaves ski.
Too stiff a boot and too soft a ski, you'll over drive the ski (skiing will suck)
Too stiff a ski and too soft a boot, you won't be able to drive the ski (skiing will suck).
Balance this and you will enjoy the package you have and the skiing you do.
I've tried to make this intentional short and sweet without giving one recommendation over another (don't worry others will).
My personal preference is on the stiffer side as I ski well enough to moderate input (so over driving is not an issue, usually), what I don't like is providing input and it not being transferred to the ski (too soft a boot). I also like stiffer skis (so stiffer boots are in order).