Rip - sorry, not biting
. I like you and you're very helpful to everyone.
OP - I advise you just to try a lot of leaders and see what happens. That's what I did. If you tie a leader of 9' and find that it turns over too slowly, don't be afraid to cut off a foot or so, or tie on a heavier tippet, etc. Leaders are cheap and you'll eventually figure out what leader works best for your flies and casting style.
If your leader comes back with a lot of wind knots, work on shorter distance casting and eliminating slack
Last quickie -- if you're like me, you might like to practice casting and go for longer distances while fishing. A level leader will very quickly show you any wind knots and can be a pretty effective tool. A tapered leader will NOT mask any problems in your casting.