Scroll only the page content?

I I have almost finished my web site using Dashboard theme, but in many “gallery” pages I have a lot of thumbnails and, when I scroll down, also the menu and sidebar disappears over the top: Record Covers
Now I have all my gallery+lightbox pages made with the plugin Weaverpix and a very good theme by Will Woodgate, so I know it is impossible to add a “scroll stack”.
But if I will decide to change all those pages using a stack gallery instead of Weaverpix, is there a stack allowing to scroll (with the mouse wheel) only the content and not the menu+sidebar?
I took a look at Nick Cates “Scroll Page”, good stack but it seem not what I need.

Heres a scroll stack from Archetypon — Scroll Scope — that may do what you want.

RapidWeaver Central

Thank you, it could be a solution, but i do not like, in this and other scroll stacks I found, the frame with scroll bar.
The best solution would be fixing the menu and sidebar of the theme, but I am not expert in codes, CSS and so on.