@lucky I don't recommend using spine-unity 4.3-beta yet, as porting is not done yet. You might want to wait a bit until it is completed at least, or continue using 4.2.
While the spine-unity 4.2 runtime is guaranteed to be compatible with Unity 6000.0, if we find any issues on 6000.1 we will very likely back-port any bugfixes to 4.2 as well, especially until 4.3 is still in beta. If you encounter any issues on 6000.1, please do not hesitate to let us know.