On Wednesday, February 10, 2016 at 5:04:33 PM UTC-5, Six-Seven Romeo wrote:
I am in the midst of an instrument panel refit on a Standard Cirrus that
will include a PowerFLARM core.

Good for you! Glad to see the turds posting mis-information on RAS ignored ;-)

The mount of the FLARM antennas is always a lifely subject here on RAS.
I have read and absorbed the very instructive
FLARM antenna placement application note.

Anyway, someone mentioned to me years ago that it is a bad idea to mount
things on the canopy or canopy rails (PDA, Camera, etc) as it could prevent
full ejection of the canopy and leave it tethered to the fuselage by a power
or control cable. This could make a bad situation worse (take that statement
for what it is worth). Truth or myth?

Truth, implicated in at least one fatality (PDA mount prevented canopy jettison).

Assuming for the moment that the above is true, then same logic leads me
to the bad idea of mounting things onto a glare screen that is attached to
the canopy like with a Standard Cirrus.

Yes, but: you can cut a hole in the glare shield and mount the antenna
on a light-weight support below, poking through the hole. Presto, canopy
can jettison freely, and you can easily remove canopy without deranging
antenna. IIRC there are examples in the FLARM note.

Hope that helps,
Best Regards, Dave