The floating review draft banners had some issues when scrolling off the

edge of a review. Due to some imprecise calculations, the page would

appear to stutter for a brief moment while scrolling, as the banner

jumped back and forth between being docked to the page and floating over

the page.
To fix the stutter, we needed to set the placeholder to have the exact

height and margins of the original banner, pre-float. This kept the

container the same size. We also needed to fix some of the calculations

to not go in/out of float mode too soon.
With this fixed, the page no longer jumped, but the banner would just

disappear as we hit the edge of the review. Now, the banner will appear

to dock at the bottom of the review, and just scroll out of view as the

user scrolls further down.
The end result is a buttery-smooth scrolling experience.

Tested on Chrome and Firefox.
I edited a field to get a draft banner and saw it docked at the top of the

review. I began scrolling and saw it smoothly undock, without any page

contents jumping. I then scrolled until it was out of view. The banner never

went past the bottom of the review, and it remained fixed there until it was

no longer in view.
(Checking the DOM verified that it did leave the floating state, yet there was

no weird page jump/stutter.)