Replying to Initial drop angle on a 7-foot high platform?

My platform is 7' up which seems pretty high compared to other setups so I'm trying to figure out what the slope will be like. What should the angle of the initial drop be?

There's a lot you can do to speed it up construction fence, dish soap, make the slope a "ladder" rather than solid but nothing I could do to slow it down if the initial drop ended up being too steep and making the whole thing too fast

I'm 210 lbs tho so maybe I could use that extra speed