I had to cut and move the supports too, as suggested above. I have a G3X on both the pilot and copilot sides
One thing to consider when doing the layout is whether you want to put a radio/nav stack (6.25" wide boxes)in the middle of the panel between the G3X's (if you have two) is to design in any rack mounting hardware, L-brackets, etc that you may want to use in the future for the panel and aft support .. and locate the new support ribs appropriately, or make them integral with the rack supports.
I had to do a bit of retrofit on my supports when I added a few rack mounted boxes -- would have been trivial to have designed it in from the start.