I noticed the following problem: When I activate the Minimalistic Header option and go to any page, scroll down a bit and the header changes to the fixed, small top bar, Firefox does a huge jump down. You automatically skim a lot of page content. You have to scroll up again, in order to see that stuff. If you do to much, another ugly jump appears.
I wouldn't need the minimalisitc header, but I don't want to see an image when the header is undocked. If I could set a solid color, it would be fine.
These jumps don't appear when minimalistic header is off.