Header element sticks, but page jumps

[RongBranovate]

I have a <header> element which i make sticky when scrolling down.

side-note: in order to make it stick i gave it margin-top: 1px like suggested in issue #132.

But when happens when i scroll down is that the placeholder div is added very violently and it seems like the entire page "jumps".
Any idea how to add that in a softer manner?

[novakben]

Same here.
not on header though.
Just a form tag with 100% width.
The page jumps up to fill to space even if I manually place
use-placeholder="true"