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Could you provide some more details, please? What exactly you want to rotate: the sheet itself, the impose block of pages or single pages? Thank you.
Owlet is a completely different rendering application available separately from Boxshot. You can use it from Boxshot Ultimate for rendering, though. The results are different, as Owlet takes much more efforts to produce a more realistic image at the price of the complexity of initial setup.
What about Lathe object? You simply draw the outline you need and get the bottle you want. Takes slightly longer than moving a slider, but lets you do anything round.
It would be nice if you provide some details on what exactly doesn't work for you?

The current implementation of shuffle is based on n-up layout. We split pages in groups, shuffle them and then do n-up for that group, then go to the next one.

If you have a look at n-up implementation, you'll find that it also acts different if duplex mode is enabled. The thing is that in duplex mode IW tries to put even pages right behind the odd ones on the sheet.

So in both n-up, cut stack and shuffle if the duplex mode is enabled, each second page goes to the other side of the sheet, not to the right/bottom of the current page. That's the difference and it lets you easily duplicate fronts to backs by providing "1 1" rule to shuffle.

We have some customers struggling with that approach, so the big question is what would be better: to add another option to shuffle, or to make the default behavior more obvious by providing some hints and helps.

Your opinion is much appreciated :)