i don't have enough trees in my back yard to hang so i want to sink some posts to hang from.

my first thought was that i'd sink some 6x6 pressure treated posts to hang from but then i decided i wanted to make it movable.

i think someone on here had used galvanized fence posts, set in concrete to hang from.

what i'd like to do is have the posts removable so that i can take them out when not in use. could i sink shorter sections of pipe, larger diameter then the size i'll be hanging from, in concrete so that i can stand the hanging posts into the holes? i'd want the concrete to be level with the gound so that when i remove the posts, i could run my mower over them.

what size/gauge of galvanized posts would i have to use? would i have to have a support pipe on the top to keep the posts from bowing in?