Snug the chain and when the flag guy at the end signals ya,
DROP THE HAMMER
Never pulled with an auto ........
4 low and I would imagine 2nd gear for the C-6 {that is how I pull} I'm sure someone with a slusher will chime in ;p
Keep your hitch height just under 21" It will be checked when you weigh in..and you will get weighed!
You just may get surprised at how much your rig weighs...I know I about choked when my truck weighed 7785
I use a solid 12k lb ring, but I have seen just about everything used so long as the sled chain can hook to it and the tech guy says OKY-DOKY
Avoid the temptation to "dig in" for that last couple inches....that is where most guys grenade parts, specially the front end when it starts to chatter.
You WILL feel when it is time to back off the go pedal.
FYI for your brother, my best pull is 266 ft with a
35k lb sled--20k sled/15k weight box...
After you lock the box at the top is when you will REALLY feel it
The first couple times I was too busy watching my boost and stack temps and just barely caught a glimpse in my mirror when the box locked at the top
It is a wicked awesome feeling !
Good luck