I would put a block at both ends and fix them so that the big PVC is off the bottom. Laying on bottom may loose so of its effectiveness, I also would tie 20oz bottles to it to keep up, up.

I know the way you have it now it will do that.

When I do a pvc tree, I can put it in 30ft water, 10ft rope to bottom of 10ft tall tree with bottle tied to top. I am now fishing in 10 to 20ft of water. I make mine with a 10ft 4" trunk and 10ft 3/4" limbs. Or if I do like you did, I take the limbs all the way through.

But I don't thing you can make one wrong. As long as you just make it.