OK, here is the beta. Please note that BD3D2MK3D doesn't check the validity of the arguments passed to x265. It doesn't warn you if you use out of range parameters, or if you encode in a format not compatible with the 3D or specific hardware. (In the other hand, some safeguards exist when you encode with x264.) Also, x265 is still unstable and heavily developed. New builds are available every days. I have included the latest builds (released today), but I can't be sure that they are bug free. So, currently, consider the x265 option as experimental, and use it at your own risk.
There are other things to consider when you encode in h265 format, such as compatibility problems. For more info, see the warning when you select the x265 encoder in the Settings menu.
Please report problems when using x265 (or x264) here, with a maximum of details. Without negative reports, I will release v0.63 final in one week or so...
Download v0.63beta1:
BD3D2MK3D_v0.63beta1.7z
(Since this version is a beta, you can still download the stable v0.62 via the first post of this thread.)