Hello,
I understand what you mean. You want the tabs title bar stay at the bottom while the Fences itself roll up. So that you can just move your mouse a little if you wish to select those other tabs, yes? 

Unfortunately, I believe, there is no option for that. However, I have forwarded your request to the Stardock Support Team for their review and recommendations. We really do appreciate your feedback.

Thank you.
Basj,
Stardock Community Assistant.

I had the same issue with fences at the bottom of the screen. The best solution I found to this problem is just to move fences to the top of the screen instead bottom and then adjust (right click the header > select "view" > select "tittlebar position" > uncheck "move tittlebar to the to the bottom when near the top of the screen")

It would be nice to see a tittlebar position option like this for the rollups at the bottom of the screen too.