What type of screws are you using to attach the bucket pieces to the 4 in PVC pipe? What are you filling the center of the 4 in PVC with? I just found a good use for a bunch of old buckets.
Are you saying that the display shows only blobs on your screen? And no definition?
The gentleman who makes these just uses drywall screws. If I were doing it I'd probably opt for stainless steel fence screws. Buoyancy is some Styrofoam crammed into the top of the tube but pool noodles would work very well. Either way you need to close the top to hold the flotation inside.
When I see one of these on my Helix screen it looks like a fuzzy cedar. Very indistinct except for the height which is usually around 8'. A typical tree with limbs shows up exactly like a tree. You would think these would show up clearly but as Rickie pointed out PVC has nearly the same density as water hence the cloaking factor. Probably not a bad thing if you want to keep this a secret.