Welshman, I agree with Pete re using a metal strap. Not a good idea. Need to use something non-metallic.
Your 9.2KW continuous goal may be tough without special cooling. The continuous power output of PJs is known to be highly overrated. The toroid heats up quickly and the attached thermistor will shut the unit down. If you can open up the toroids and improve the airflow, you may have shot at 9.2KW. Otherwise, 35-40% of PJs stated power output is what you should expect (continuous).
At 3KW, my PJ 8000 (24v) toroid is very hot to the touch. Granted, you're running 48v so current should be half what runs through my single toroid, and heat will be further divided by your two toroids. So, maybe you've got a reasonable shot at it.
A note about the batteries. My PJ holds output AC voltage quite good. But, as the battery voltage drops, DC current must increase to deliver the wattage. As the amps go up, battery internal resistance increases and the system works harder to meet your needs. And the battery voltage drops faster and faster toward auto shutdown.
I'll try and find the "adjust resistor" on mine this weekend. I'm not sure our control boards are exactly the same.