Hello!
There is a general opinion that it is not possible to edit Ultra HD 3D videos in full side-by-side format with Sony Movie Studio Platinum 13. However, it is possible to do that without having to use Vegas Pro version. I've just uploaded tutorial on YouTube how to prepare 3D Ultra HD videos, how to edit 3D UHD clips and how to export them (including full side-by-side UHD = 7680x2160) by 3D converter and Sony Movie Studio Platinum 13:
Note that the first 16 minutes of the video is the most important.
Maybe the tutorial can be useful also for those dealing with HD clips as well.
The most important conclusion is that Sony MSP 13 can import full side-by-side UHD clips (7680x2160) if they are encoded by UT codec.
Some other tutorials about 3D converter can be found here:
https://www.youtube.com/channel/UCL9azB3Y1w9R2cv3r1gK5rg
Damir