You wanna cover your pots with leaf and sticks and other debri so from the ground they look like squirrel nests. Then secure your pot or bucket with a semi mature plant already in it in the tree. The sun is very strong at the canopy like this and a young seddling or clone will burn up! Attatch some black vinyl tubing to the bucket at the soil surface for feeding and run the rest of the tubing all the way down the tree to the base of the trunk, you can camoflauge the tubing with vines. Then all you need is a battery powered water pump capable of moving water x amount of feet straight up and some good nutrients and your in business!
Ive actually heard of people postioning multiple buckets on branches below the top bucket and using the runoff from the top bucket to down to the buckets below thru a hose that comes out of a hole drilled in the bottom of each bucket.
Either way using a pump to feed is going to make tree top gardening a helluva lot easier and safer since your cutting down on all those climbing trips! And if ya think about it you never hear about cops busting tree top gardens either! Ive never heard of it happening.