Well I hurt my back yesterday so I didn't get up and work on the plane. By this evening it was feeling a little better so I started laying out the exact location for the avionics so I can cut out the holes. My panel is pretty simple with 1 EFIS, 1 GPS/MFD, 1 backup EFIS, and 2 radios. The makes for 4 holes (the radios go into one square hole). The nice thing about this is working indoors - it was 15F outside. It was slow going, but I got the reference lines layed out. Precision is key here or I'll have tilted instruments. Plus you have to accomodate how the panel mounts which chews up an inch around the top and 13/16ths along the sides.
Marking reference lines on the blank instrument panel.
The thin lines are probably not visible in this photo
My stack - Garmin GNC-300XL IFR GPS/COM and Garmin GTX327 transponder