Elliot Sloan has a huge vert ramp in his backyard, along with a megaramp complex. It's one of the most epic things to skate in SoCal.
I've skated it a few times, and it's well over 100 feet wide, and significant parts are over 14' tall. However, I don't know the specs. Here's a video of me skating the vert ramp in 2014:
Ryan Spence did significant design work on Sloan's megaramp. (But who built it? What are the specs?)