Colyn writes: <<<Brent,   Not sure what you meant by OR Did you mean you are okay with certified efis and no spinning mass? Or did you mean you must have certified efis AND spinning mass?>>>>

If you have a certified system with an engineered STC'ed  installation and level A software then your EFIS is legal as your only instrumentation. For me, I would still have a AH, AS and Alt.

Google Air France Flight 447 to know the reason why.

Regards
Brent Regan