"I have not seen one yet that has signs of wet stacking. So they may be very resistant to it."
I agreed with everything you said until this statement about wet stacking. IF you under load these sets they WILL wet stack like crazy. I have seen hundreds and corrected the problem by the only way possible. Run the set at full load for 6-8 hours.
That's the good thing about most of your load requirements. You need/have a relatively stable load, whether its 5 KW or 10 KW. You plan on using a generator that is close to your needs. The Military has another kind of mindset altogether. If the max load requirement is 4-5 KW, the military will allocate a 10 KW generator for the job. A perfect case in point were the Duck Hunters, (Air Defenders) during the heyday of HAWK low to middle altitude, Air Defence System. All the generators ran at 30-45% load. Wet stacking was a big problem. To compound it, and prove that no one could learn from the problem, along came PATRIOT Air Defence. Each firing battery had 6 launchers. Each launcher had a 15 KW, MEP-113A 400 hz generator mounted on it. The sets ran day and night to power up the launcher. Max load? 4-5 KW. The Exxon Valdez oil spill had nothing on these sets. So when the launcher suddenly needed more of a load, like to fire a bird, the generator sets dropped off line. We would receive them in our work shop and have to run them at stepped up loads until they could pull at least 15 KW. Usually took 8 hours of full load to clear it up. When PATRIOT went to the 15 KW, MEP-814A, 400 hz model, same problem. You are never going to run a set 1000 or 1600 hours at 20-40% load. Most of you are too consciences to do so. You know your requirements, and you try and stay close to it with the right generator set. But beleve me. Wet stacking can be a problem if you allow it to happen.