homemade honda 2000i paraell cable
Not completely safe. 2 EU2000 will put out over 30 amps, which is a bit much for a 20 amp socket and the matching plug, plus perhaps the circuitry that the 20 amp plug services. If you have only 1 EU2000, than a 20 amp socket is perfectly fine, but in that case you don't need a parallel cable, just an extention cord.
With electrical circuits, the 'weakest' component is the one to watch out for. In my case, I often run my 30 amp trailer from a 15 amp socket, BUT, that socket is fused for 15 amps, so I never exceed the 'limiting' factor of 15 amps and if I do, I'm protected. Your case seems a bit more confusing, as you imply that 20 amps is your limiting factor, but you need 'extra wattage'.
Everything depends on what you are powering. If it is wired for 20 amps, then providing it more than 20 amps will likely cause problems (blowing fuses or causing fires, depending on how well it is wired). One possibility, if you really need more than 20 amps and can 'rewire' your loads, would be to use 1 source (generator) for some circuits and another source for the rest of the circuits. Again, in this case, there would be no need for a parallel cable, since the two generators and their loads would be completely separated. If done intelligently, you could have one for stuff which needs to be 'always' powered and one for those things which need 'occasional' power.
