I made my mid/high absorbers with just one 2'x4'x2" panel of mineral wool.
For some reason I was thinking they only needed to be 2" thick.
Is this OK or should I make a couple more using doubled up panels so they are 4" thick??
I have the 2" panels spaced off the wall about 2".
The room will primarily be used for recording acoustic guitar so I want it a little lively.
And again the room is 11x11x8.
I've treated all the corners with 4" thick mineral wool bass traps.
If I make a couple of 4" mid/high absorbers will it make a big difference in the sound of the room?
Will it make the mid/high absorbers a lot more effective at absorbing bass and mids and highs?
I appreciate any advice.

I'd double them up if you can. When dealing with reflections, it's almost always best to use the thickest material you can so that you don't simply mess up the spectrum of the reflection.

Well, I made one 4" mid/high absorber and put it up spaced about 2" off the wall. I put it near the bass trap in my "trouble spot" corner. It now sounds VERY balanced. I think my room is ready to start recording in. GOD BLESS YOU GUYS!
I appreciate all of your help.