I haven't had much desire to work on this project anymore, there are some alternatives out there that are much cooler/better, check out TreeGravity by Dudenn on SpigotMC
BigScary created this plugin to fix the "floating treetops" problem. When players chop a layer out of a tree's trunk, the rest of the tree falls down to rest on the remaining stump (any branches fall to the ground). This ensures no tree blocks will be left hovering in the air. Players who don't like it can disable it, unless that toggle is itself disabled by the server owner.