I've collected like 15-20 free trampolines, from 12-15ft diameter. You get 2 full arches out of every frame ( I go a max of 8-10ft between ribs, fence top rail pipes work good as connectors), and they make the best temporary hoop houses I know of. Already have the fittings built right in where the legs went too, just add pipe! They even hold up with 2-3 ft of snow on top! I've raised them an extra few ft with side poles, for more ceiling height. I make carports and all kinds of structures out of them. You couls even do quarter arches of the frame, and make a lean-to like shelter right up against a house. Can't beat free pre bent galvanized arches. Some of the trampolines are super high quality, with thick steel and solid re-enforced connections! Anyway...
Being on your porch, I'm guessing whatever lightweight portable canopy like deal you use might end up on the neighbors roof, especially it you don't cinch it down good somehow during storms. Good luck!