Richard writes:

<<<Does that
not give the Administrator discretion to approve an
EFIS-SV for IFR navigation? >>>

In theory, yes. In practice you would have to demonstrate to the Administrator that your airplane met certain minimum standards. I believe the process is called "certification".

The EAA has some relevant information at the following link.

http://members.eaa.org/home/homebuilders/faq/Equipping%20a%20Homebuilt%20for%20IFR%20operations.html

Regards
Brent Regan