Yes I know this plugin, and have ever wanted to implement the support of it, but usually had more important features to complete first… My pathfinder supports no caves, only a heighmap like terrain (made of landscape and static meshes), thus I talked with its creator, he promised me once he is going to make a more simple deformable heightmap terrain plugin too… Only question of time and money 
Anyway, if the voxel terrain collision channel is set to my custom terrain channel it must work, what I need to implement is runtime area update (measuring and storing terrain surface height and slope data), which is not a huge problem.