Question:

I've specified 'static' persistency for my layer, but the layer doesn't stand absolutely still when scrolling: it 'flickers' somewhat. Can that flickering be avoided?

Answer:

I'm afraid some jumping/flickering can not be avoided.
There is a CSS way to make layers stick to a fixed position in the window (see http://devnull.tagsoup.com/), but it is not compatible with older browsers like Netscape 4.x.
Furthermore, CSS can't make a layer move only when it is about to be scrolled of the page.