make a platform to go on top with 2x4 attached to plywood. then make the support section, but instead of putting in screws or nails on the pieces of wood connecting the front 2x4 to the back ones, use bolts and screws so its collapsible. then, just make a the drop in out of plywood and 2x4s and attach some metal hooks on the top so you can hang it from the front of your drop in.
i think he means in-run room. like with a drop in you need like 15 ft before the jump, the bungee is more like 50ish, depending on the length of the bungee
im building this for my yard, but mine is like a scalene triangle. 10 foot ladder, not straight up though, then 14 feet of ramp, on a hinge. and it takes 13.5 ft of space. il post pics when its done