RE: First runs on F-Type 158 + 11.0
The others here have given you some pretty good advice.
Is your stance different from what you've been doing (like does it feel weird to be hanging so close to the water) or are you actually dragging your butt in the water?
I agree with Rod, on the boom height. Unless you are on a true formula board and racing upwind downwind formula courses, placing the boom up much higher than your chin is probably not necessary and may be giving you some imbalance.
I thiink Rod and I went through a whole series of posts a couple of years back where he started out with the boom too low, then moved it too high and eventually he found that at about chin level (where I tend to run my booms on wider boards and larger sails) seemed to balance out the best.
Then you need to either use adjustable harness lines (I favor the Sailworks Quik-Tune lines) or get a set of lines in a length that makes you most comfortable where ever you set the boom height.
Double lines, for mostly back and forth reaching are probably not necessary as you will rarely go deep enough off the wind to need the really long lines and rarely go high enough upwind to need the super short lines. The adjustables are a nice feature as you can "tune" your harness line length for whatever the conditions need, at the moment and on the fly.
The adjustable outhaul (whether a simple single side version like Rod is using or a full on double side formula setup) is as you are finding, almost mandatory for sails larger than about 9.0 m2. Without the adjustable outhaul, you are going to find yourself overpowered and underpowered alot of the time. With the adjustment you can tune your rig for the conditions as they change.
You really need a bit more "time on the water" to sort out the differences between what you've been sailing and the super wide F-Type 158 with the big 11.0 m2 rig.
It's going to take some time for you to figure out how a large rig balances, how to tune it for different conditions, and how you need to change your stance to get the best speed and earliest planing from your setup.
Hope this helps,