FWIW, fully a quarter of the screen is taken up by fixed position elements that are entirely irrelevant to a reader. When I see this on sites I want or have to use, I add cosmetic rules to delete the sticky elements. When I see it on sites I don't have to use, I close the tab.

I don't claim that this makes it a net loss for you from a money standpoint, nor that I'm representative of a majority of your market, but I _do_ suspect I'm the sort of potential customer that isn't easily studied in an A/B test.

Cheers!