Jeff Liebermann wrote:

...
... The thermal resistance of the flange mount was too high for
one device to handle the load at the rated temperatures. However, 4
devices did the trick.

Barry L. Ornitz, PhD WA4VZQ

Yeah, all that, and then try to sink 5KW+ into a paint can ... 20 X 1000
ohm resistors is very minimum, in a tubular aluminum heat-sink-no less,
in my humble opinion ... as when you are in key-down, and your attention
is diverted, things can get warm, quickly, or so it seems!

Regards,
JS