Don't bother with the splash guard until you get this tranny setup correctly.
Get that tranny down as low as you can get it and then set an angle like you have and take it for a run.
Keep playing with the tilted angle until your picture is good at speed and when you are happy with it, start lifting the tranny a bit at a time until you start losing the picture again.
Drop it down a touch again to get the picture back and then fit the splash guard if you are getting a rooster tail.
The secret here is to bury that tranny deep into the water and get that angle setup correctly and then you can start playing with the height.
Splash guards and rooster tails should be the very last thing on your mind at this stage.