Pat:
I agree with Jack that you have to pursue this diligently with the FSDO avionics person. Directing him/her to the following website may help:
www.consultresearch.com/EFIS.htm
It has a draft letter to the FAA making the case for allowing such installations. You can make the argument just as well as I can, except that here it's coming from a third party (an aerospace engineer who has worked with the FAA, consulted for GE and has no ax to grind) and this site has everything in one place, not just the arguments but also pictures of the units, links to the manufacturers' sites and a link to a harrowing fatal accident that could have been avoided with these units.
I need to warn you that I think some of the newer Garmin handheld units weaken the arguments expressed in the letter. I drafted the letter earlier this year with the intention of starting a push at the FAA for blanket approval of experimental EFIS units. But certain developments since then, including these Garmin units, have led me to reconsider. I still think they should be approved, that it's a no-brainer. But the Garmin units include a "panel" screen, which is a GPS-derived version of an aircraft instrument panel and provides much of what you get with an EFIS. Enough, I believe, to get you out of trouble in IMC if you lose all your aircraft instruments (the sole exception is true airspeed, but I think ground speed is an adequate substitute). Frankly, this is not my expertise and I've been reluctant to argue that EFIS is critically needed if the FAA can argue that inexpensive flightbag instruments can do the job.
I have discussed this with several people (if the Garmin handheld "panel" screen is an adequate substitute) and:
a) I get opposing viewpoints, and
b) have had difficulty getting others to discuss it.
This uncertainty has weakened my resolve to pursue this. I raise it because
you should be prepared to address the issue if the FAA inspector brings it up.
Ernie
P.S. BTW, I would welcome views on this matter of the "panel" screen being adequate.