Another thing is look at the efficiency numbers with the short fore-aft aircraft antenna, and you see a major part of the output just heated up nonradiating elements.

Another point us, you don't have to run them at spec or over-spec power! In fact i read about this in some U.K. ham magazine where someone was doing this years ago. I recall when i bought an ATD some decades back, the seller told me he tested it worked with a B+ of about 100 volt. Of course that's grossly inefficient, considering the filament draw, but if you need efficiency, AM CW radio is not the means.