Garmin G5 or similar EFIS

I installed the experimental AV30 just for the reason Larry said,

Thanks for the prompt reply, Larry.

Thanks for all the feedback about 4-point restraints.  My next question deals with the G5 or similar EFIS.  When I first bought my 415D last year, the previous owner said I could install the experimental version of the Garmin G5 ($1000 dollars less than the certified version) because the Ercoupes were built prior to the advent of TSOs. My hangar manager, who is an A&P, is not so sure.  I asked another avionics tech and he didn't know either.  Any knowledge out there on this subject?  Thanks.