Hi j-d,
I successfully run one 13500 on 15 amps. By definition 30 amps is twice as large, therefore running 2 13500 on 30 amps may actually be easier than running one on 15. The compressor start ups are not likely to coincide.
It is true there won't be a lot left over for other purposes. So I would do as I have done with my water heater. I added an additional shore power cord with male and female plugs so I can switch back to the OEM wiring in 20 seconds if I so wish.
The real risk is low voltage (brown out). That can be solved by adding an autoformer.
Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp-hours of Telcom jars, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.