The position to the right only works 1 of 2 ways. Either static or dynamic. Dynamic will only display tabs in the "Canvas Main Right" position if the first tab in the "Canvas Main Middle" position is selected. Static "Canvas Main Right Static" position will always display regardless of the tab selected. There is no functionality for what you're wanting (dynamic based off a specific tab).
The only way to have what you're wanting is probably a Custom HTML field that substitutes in your tabs inside of custom Bootstrap grid usage. Example as follows.
Code:
<div class="row">
<div class="col-sm-8">
[cb:usertab tab="TAB_ID" formatting="divs" /]
</div>
<div class="col-sm-4">
[cb:usertab tab="TAB_ID" formatting="divs" /]
</div>
</div>
The above uses tab substitutions as documented below to substitute those tabs into a field.
www.joomlapolis.com/documentation/279-community-builder/tutorials/18353-using-substitutions-throughout-cb
For Bootstrap grid usage information see the below.
getbootstrap.com/css/#grid