You will have to work the numbers, will you get enough out of the 2 1600 units to start the ac? My 2400 yam sometimes will have to take a second go at it, if the capacitor is empty and rusty. Thus the need for Honda guys to need two 2k units to get 3k to run.
Although, some days I wish I had two smaller units as to the 2400. For convenience like you said.
If there fuel system is like a Honda it's an easy and cheap fix for the lack of fuel capacity. That is the one downside to my Yamaha, up until about a year ago the was no extended run time option, due to being gravity feed. And the kit they have now is pricey.