Added a removable bed platform to be able to sleep in the car with the A/C on powered by the High Voltage battery (how to turn Auto Engine Off steps at the end of the video). Support frame , template, and foam mattress. Notes after the 1st trip:

25% of battery used overnight while level 1 charger plugged in

Boyds Campground in Key West actually has 30amp plug for using with level 2 charger even on their small site, even though they told me there is only 110v plug, there are both.

AC worked fine through the night, but the car is much warmer in the rear. Sleep with head towards the front, and maybe bring a small fan (perhaps USB powered) to circulate the air around the car better.

Portable shower is awesome, but 2 gallon water tank not nearly enough, barely lasted a couple of minutes.

I should have listened to advice for blacking out windows with reflectics. While having ac was great I could feel the heat coming especially from the rear window even with well tinted windows.

Playing "Tetris" and having to move stuff from the back seats to the front seats to make room for sleeping and back is a pita. Most van life folks complain about this, but CMax is so small even for a 2 day trip this was annoying. Although for 1 person would be less of an issue as you could leave most stuff in front passenger seat.

If your campsite has power, bring a cattle to boil water.

Have a flashlight handy, bug spray, sun screen.

Power strip and multi port USB charger are really useful, since CMax has 110 plug inside, a lot of small electronics can be charged if you bring a power strip, and even better a multiport USB charger.

Run a line/wire/rope from the 2 hangers above the rear doors inside, can be useful for drying clothes or if you have a 2 in 1 laptop that flips over or a tablet with a similar flip cover, you can hang it on the wire/line and make a little movie theater. We enjoyed watching a downloaded Netflix episode while it rained for a while.

If you have room to bring a small battery vacuum that could be useful, or at least look for rubber floor mats. It took forever for me to clean out all the sand/camping ground dirt from the car.