When you work in Stereo3D in Mistika Boutique, what you normally define in MistikaSetup->Master Format is the render resolution for each eye.

But the final render will also output that resolution by default. This means that if you want to render in Top & Bottom mode and with both eyes at full resolution then you need to activate the Rescale option in the render panel and duplicate the Y resolution.  In this way, the two eyes composition is done as a post-filter  after each eye has been rendered, which provides the best quality.

Otherwise, if you do not use the Rescale option as said both eyes will be "squeezed" into one image at the original master format, thus reducing half the vertical resolution of each eye (in some cases this is useful to reduce bandwidth, but it is at the cost of image quality) 

Example:  Let´s say that we want the render resolution for each eye to be 4096x2048, for  a total Top+Bottom resolution equal to  4096x4096. Then:

1 - Set MistikaConfig->Master Formats -> Render X/Y to 4096x2048.  And do all your interactive work at this resolution

2 - When finished, go to Output -> Render->Video (Settings Wheel)  and set these options:

- Stereo mode-> Top & Bottom

- Scale: On

- Scale settings: SizeX=4096 , Size Y = 4096

From this point you will see this message on top of this panel   Resolution: 4096x4096

Then you are ready to render. 

Note: Those settings are persistent for posterior renders. When the scaling post filter has been activated it will be indicated with a "Scale active!" warning in the video settings. Once you do not want to render in stereo Top & Bottom anymore remember to deactivate the Scale setting!