Another Forum answer.
Possible to connect two inverter generators to one L14-30 socket?
"That's what I was wondering about. The kit that Yamaha sells for the EF2000is is essentially a box with an L5-20 receptacle (a 3 prong 120v receptacle) and and a set of plugs for each generator. It basically ties both hots, neutrals, and grounds to their respective ports on the socket to double the output from 13 amps to 26 amps. The inverter in the generators is what allows them to do this, they'll put out 120v/60hz consistently even with the engine idling, and actually have electronic throttles that can change engine speed depending on load. Standard generators can't do this since they need to run at a constant RPM to achieve 120v/60hz, and any variation in engine RPM while they're tied together will result in a fireworks show."
Sounds like 2 inverter gens may be possible.
Again, check with manufacturer.
2016 Toyota Tundra SR5, 5.7 V8