E.D. - Don't hold me to this but I could swear I read (albeit quite a while back) that Van's provided a builder with a panel section that was just the blank panel prior to the cutouts being made.
I can see Van's not wanting to give out their CAD info .... but have you asked Van's if they would be kind enough to pull the panel section(s) you need from the manufacturing line prior to making the avionics cutouts?
RV-12 Wings, Empennage, Fuselage, Finishing, Avionics and Powerplant kits all completed
Dues paid until September 2019