I have had and used a number of similar sized Bird loads through the years. I
have run as much as 2000 watts CW for short periods with no ill effects.
While visiting a fellow ham years back, he was tuning up a Henry 5K at 4000
watts out into a similarly sized Bird load, again with no ill effects. It would
appear that they are very conservatively rated especially for short duty cycles.
Hope this is helpful.
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