Would the 27 work for non-touch?
I have the non touch G3X system and I installed a separate bus and switch for it. When I turn the master on all my radio, transponder, engine monitor and things like that come on. After engine start I flip the avionics (G3X) switch on and everything works fine. I also have a Dynon 10a with backup battery and a 660 GPS with battery as my G3X backup.
I have a separate engine monitor, already there before the G3X upgrade, so this works for me. I guess it wouldn?t for you. Best to install a backup battery system for your G3X system so it will hold power on the system during engine start.