Replying to Minimum summer rail length for learning tricks

Basically I’m building a summer setup on a slope that’s 30-35 feet long. At the end of the runout is a very steep slope that I really don’t want to fall down so I’ll be leaving at least 8 feet of space at the end.

What I need to know: what’s the shortest rail I can learn tricks on. I’ll be cleaning up my all 8, learning spins on and the hardest thing I want to be able to land is 270 on, swap, 270 off. Also it’ll be a downrail so I can’t just slide it mega slow.