The only trouble is, you'll have lots of wastage from the 5' wide lip. Plywood comes in 4'x8' sheets. But other than that sick, or you may have lots of scrap since your dad is a Carpenter.
PS: You can use mine any time you want too. It's in my back yard, but it's only 4'wide x 8' long x 4' high. Not as awesome as yours but a perfect lake jump since it's so portable!
trailsguy.pinkbike.com/album/DJStreet This the the lake jump. 4' is awesome and you won't have as much wasteage, plus both edged will be factory which makes it look super clean.
Rounded for sure haha! The ply will be curved in a perfect circle. I hadn't set sketch-up to smooth out the circle when I drew this. Figured it out later.