Hamid:

Thanks for the feedback on the 12V switching supply design.
I understand and appreciate you comments on I vs V and efficiency.
Really, I'm not that concerned with efficiency per se, but rather
whether or not I will need a fan or heatsink. I think I will not
due to the relatively low loads from my panel. Will take error
conditions into consideration also. One concern I have is EMI
radiated or fed back through the input wiring. Will try it and see.

On the bench I can test the supply under a variety of load
conditions, as well as temperature, humidity, vibration, ESD,
and EMI. I plan to submit one unit to temperature and humidity
torture testing similar to our commercial products. My employer
doesn't build or test to DO-160, but we do ship a few million
units a month into consumer electronics at high 99+% yield.
It's a different environment, but does require solid engineering
to keep working when everything else is out of spec.

One minor addition to your comments. The 0.1 lbs quote is, as you say,
no enclosure, no heat sink. But it is for the 12A continuous, 15A peak
design, not the 5A reference board from Linear Tech. Most of the
heat sinking/spreading is via thick copper on the PCB. The datasheet
indicates "95% typical" efficiency. We both know what that means.
There is at least one unit that under one set of conditions achieved
95% efficiency (plus or minus any measurement errors and rounding
errors by the guy in marketing).

-bob