My advice. You have taken up a large amount of prime real estate at the center of your panel where your eye works the best with non visually necessary items. For starters I would say, as others have mentioned, don’t put something you have to look at for more than a millisecond down low. You need the gps screen high in your view so that looking at the screen does not require mental, or even physical, gymnastics.
Having said all that, my suggestion involves some reworking of your panel. It may seem that sounds like a headache but in reality your panel does not seem that difficult to move just a few items around to make things work. So, first, I am assuming in the center of your panel sits three knobs for dimmers (if that is incorrect please correct me), along with panel light switches. That is prime real estate for a gps. Without knowing how much space is available for those switches and dimmers, you could move those all down toward the bottom of the panel above your throttle quadrant. Also, look at the possibility of reorienting your vertical Dynon radio, knob, etc., panels to a horizontal mount instead of vertical mounts. That could free up space in the center of the panel. (I was able to see your first mock up but not your second one.). My suggestion is pretty close to your first mock up with added idea of moving your light switches down to the bottom of your panel.
Of course, all of these suggestions depends on support ribs and their location behind this equipment. I understand you are hoping to not have to cut a new panel to include an additional instrument. However, I think it is possible you could still keep your existing panel and repurpose one or two holes and add one or two holes for moving switches.
All of this is my suggestions just looking at your picture but I do think it would not be as much work as you think. Feel free to ask me to clarify my thoughts if what I mentioned needs it.
