what can I expect by adding a second 18KPV to my current 18KPV?

I've had my 18KPV on line since late August and have been really enjoying it and being off grid as much as possible.  I've had a second 18KPV setting in the shipping container since then.

Yesterday, my wife and I hung the second one in the garage, approximately 8 feet away from the first one.

The communications cables don't appear to be long enough to reach, can I make my own, longer cables? Are they the "standard" ethernet, or do they do a "crossover"?

My plan is:

A. hang second inverter in garage with welded supports, and the bracket welded to the supports.  (it is a metal garage.)

B. supply power from the existing battery bank.

C. attach the WIFI and begin communications.  Update one or both of the inverters. CALL SIGNATURE SOLAR IF/WHEN NEEDED  for assistance?!

D. make the first inverter main and the second as slave.

E. make sure all settings are in sync.

F. supply grid power to second inverter using a 60A circuit breaker.

G. attach output to subpanel in garage using 60A circuit breaker and energize.

So, my question is: I always thought that I would have enough needs for this second inverter.  Last week with four of EG4's 12000 BTU heat pumps, our hot tub, plus two 1500 watt space heaters for our shop (required because it is an unheated shop (40x14) but our water softner is in there and requires the pipes to be above freezing. I have ONE infrared heater directed to the  water softner. The second is a 750 BTU heater located in a bathroom in the garage.  The garage itself is heated via a infrared tube gas heater that keeps the 50x40 garage area about 60 in single digit temperatures.)

During last weeks cold snap I hit 13K out of the 18KPV for a couple of minutes.  The lights did flicker a couple of times while we cooked dinner and made coffee.

1. The second 18KPV should give me plenty, should it not?

2. Am I missing anything in the above steps?  Current solar will be unaffected, but needs to be updated because of deep shadows during December.  Plan on doing this during the spring/summer.  Too late in the winter, too cold for me, to do it now.  New solar WILL go into the second 18KPV.