I checked the generators with the small plug in and all the regular sockets on each generator showed "open neutral."  
When I put them both together with the parallel kit and then plugged in my surgeguard it ran through its cycle and showed everything was ok.  However, when I then plugged my trailer into it, it shows "reverse polarity"?  
Any ideas why it would be all green until I plugged my trailer in?  
Could it be reading something from the trailer?  I've run three years without a problem with the trailer side.  
Could it have something to do with the floating neutral?