Thanks for the update. The 'unique' nature of forest objects and the floating issues we've seen have been dealt with in WRPtool via a 'skewing' function that fits the forest sections to the terrain. This is only called if you use the forest placer tab on the region tool.
Your idea about using the general region tool for sparser forests is an interesting one, maps may look a bit funky if you have triangle shaped pizza-plugs all over the place though. You may want to consider making 4x ~ 9x blocks of forest using the forest placer, then copying and pasting those blocks around for a similar effect.