I upgraded my RV-8 this year to a dual Dynon HDX Skyview system and used The Dynon Fast Track universal mounting trays. With the exception of the ADAHRS, I was able to mount all the Skyview components behind each screen. The ADAHRS was mounted in the rear of the fuselage.
Not all RVs can use the universal mounting trays, but they work exceptionally well on the RV-8s.
In the picture below you can see the all the components. I moved the backup battery to the inside of the tray prior to mounting.
I also used a firewall penetration kit similar to the one referenced by Carl.