Tall shade structures

[oly14]

I'm considering building a taller shade structure (~12 ft to shade my box/camper truck) and I'm curious what others have successfully used. 1" EMT is often mentioned but those structures seem like single 10' sticks, or typically shorter than 10'. I found an older post with Elliot's cover for Millicent (viewtopic.php?f=277&t=63188&start=4) but he used old construction scaffolding, something I don't have access to. YSBW mentions 1 5/8" or 1 7/8" fencing posts "for shade shelters for Horses, Rv’s, Boats, Trucks, Cars". Before I head down the fence post path, I wanted to see if fencing posts are Playa Tested© for tall shade structures or if EMT has successfully been use for that height. If it's fence posts, terminal posts for the verticals and line posts (or top rails) for the horizontals I presume? Thanks.

[FIGJAM]

The pics on YSBW of those big shades are using top rail for everything.

Should be fine and they'll be long enough.