D.I.E.D....
Theo....excellent point; more of the stuff I have come to expect from you, thanks. The roadway that we built around the perimeter is fairly substantial; you should be able to whip that fly rod with no issue. ;\) The road, tho, is along the steep side of the pond where the shoreline is is 3:1. S'pose that this is still OK for a cluster of 3 trees? Maybe set the bottoms (5 ft tall) at about 8 ft deep?
Ewest...your Linkapalooza parties always deliver...and sell out! The topo map is pretty high on the priority list. Soon come.
Eastland...the bowling ball spheres continue to be the highest level of ingenuity I have seen, but this bucket thing whips together pretty quick and reasonably cheap, too. You're right, they are heavyweights...I think this is an advantage, along with the upright design. It will allow placement in a hole in the bottom, about 1/2 the height of the bucket...very stable. Then, every inch of the PVC limbs will be exposed, even after years of soil movement in the bottom as it may silt over somewhat.
Burgermeister...about a year ago, a new HD opened in an adjoining town and one of the promotions was these buckets for $1. I bought 10. I wish I had bought 30. Another thought: I have a pal in the building trades and he is good friends with the owner of a drywall taping business. He once told me that if I am ever looking for 5 gal buckets, well.... WRT the conc mix, I just poured the entire 60# into the bucket, threw in some water, mixed it with a spade shovel (narrow point to get in there), and then pushed the pre-drilled 4" tube straight down into the slurry. Level it by "eye" and let 'er dry.