CAD software for panel design

I would second what Dave said, and add: Before you cut your panel, make or get made a laser cut plexiglass versions of it first. It can be flat. Stuff it with instruments, stick it in the plane, turn it all on, and pretend you are flying. Your second plex version won't be the same at all... and when you do your final panel, everything will fit, be visible, be reachable, not interfere with other controls, be seen under the glare shield, have enough space around knobs to actuate, have the bus bars in the right place, have room for the bottle(s) behind the panel, etc, etc, etc...

Have fun! I did.