PBR's version of babying the engine and launch may be different than yours! lol "You're results may vary" as not too many on here leave with the front end 2 feet in the air!! (Some probably wish they had that option!!)
I've shifted my 408 at 6700+ and it runs the same number as shifting it at 6200. So of course I shift it at 6200. My engine is cyl head limited with a cam to match.