Which feigao for summit (multi purpose truck) on 4s?

[R00ST]

I have a summit I want to use for a bit of crawling/extreme offroad use. I also will be doing street runs (p2's, slammed on phalt lines or the like).

Which of the XL Feigao's would be best suited for 4s voltage?

Since I am only running 4s I want to make sure I get enough rpm but torque is key for running the big heavy canyon stock tires (can use gearing to get the speed in street trim).

7XL? 8XL?

Any input is appreciated