I run a single red top for now as well. I have found a few things help the effeciency of the fridge, and mine is the older motor design that isn't as effecient.
If the stuff is cold when you put it in, you will use lots less power.
Bringing the fridge and contents down to temp with 120v at home.
Keep it pretty full.
I keep my fridge mostly set on "1"
I use a cheapo food thermometer to monitor the inside temps and set the control accordingly.
Maybe you knew all that but for what it is worth I have had my fridge on for a few days in a row and it still started without issue.
Have fun, simply the one accessory that I won't leave behind!
My rig... "Maude"
1976 FJ40 with some stuff and some leaks.
1999 UZJ 100 Series bone stock ready to rock AKA:The backup minivan
2012 Toyota Sienna Minivan, fastest Toyota in the stable.
My camping trailer build up thread.
"You 80 guys are just a Sawzall away from nirvana." -Red Chili