@dimasic
Ah, I see what you mean now. Well, setting BBox doesn't cut out that part of the page, and shows only that - it's only used to decide how to position the existing page. You see the white margin on the right, because there is space for that part of the page to be shown on screen.
It just isn't supposed to work the way you want it to.
That said, why would you want to use fit-to-height anyway? Isn't it more natural to use Fit-to-content-Width?
Fit-to-content will be the same as Fit-to-content-width if the content is wider than it's high, and vice versa - it will be the same as Fit-to-content-height if it's higher than it's wide.
You have one other option - you can set the background colour to white in defaults.lua, instead of default gray
.
Regards,
Kai