Rated 4 out of 5 stars

I have 1 complaint/suggestion. It has to maintain the size of the header pane between emails and perhaps allow enlarging it beyond the size allowed by default by Thunderbird (perhaps remember the scroll-state so that it always opens focused on the same part of the header). Overall on the right track.

Rated 5 out of 5 stars

Works fine in TB 14Beta, if one will add in userChrome.css :

#msgHeaderView, #msgHeaderViewDeck {
max-height: 450px !important;

where max-height should be adjusted to your own requirements!

Rated 1 out of 5 stars

Resizes the header bar as promised, but the resize is useless: the same chopped off headers are displayed, with extra empty whitespace at the top. You can even see the original header box just floating down with dead space above it.

So, does resize as promised, but the resized area is just empty useless space...

Rated 3 out of 5 stars

It works fine in TB 6. But if you have several recipients in TO and one or more in CC, you cannot enlarge the header pane sufficiently to see the recipient(s) in CC without using the appearing scroll bar.

This review is for a previous version of the add-on (1.0).