I’m making my own rn and I don’t know exactly what my measurements should be. How wide and high did you make your lip? And how high was your rail for comparison?
I recommend following this tutorial he did go a little heavy on the supports, so I removed on on each side of the tower. In addition it was running a little slow so I found a cheap box of M Snow on Craigslist and added it on to the bottom.
The rail is 18 inches high and I have plenty of speed for it. I'm also pushing off the top railings of my setup like a slingshot.
There's a lot of stuff on Newschoolers "build a jib", but you need to search it separately. In addition, just start building because almost everything works and you can always make modifications.