Honda Generator

It will "work" but you will not get the full potential out. You can only pull as much power as 2x the lowest rated generator. If you pair anything with a EU1000 all you can use is 2000w. If you pull more than 2000w you will put the smaller generator into overload, as they don't have the ability to limit power. So a 3000w a 1000w has just become a 2000w generator, less than a since 3000w alone.. Pointless.

So,yes it will work...but it's not a good or practical practice.

Honda will still tell you not to mix-match.

I totally disagree with this explanation. For each generator, as its power output goes up its output voltage goes down. This causes the load to be shared based on the capability of the generator, not the absolute power level. With perfectly calibrated inverters each generator's output voltage will be the same at rated power, meaning each one will supply its rated power without the other one overloading. From user reports we know that the inverters do vary in their load-voltage curve, and even the equal-size generators don't always share the load equally. This applies just as much to matched generators as to different size generators. A Honda inverter generator has no knowledge of what the source of the parallel power is. As long as the load-voltage curve of the parallel source is compatible (and the frequency is correct), the generator is "happy".