Ok, this is what you do:
Locate your profile directory for Firefox... in the case of Windows, it'll be
C:\documents and settings\{user}\application data\mozilla\firefox\profiles\{profile}\
In there, go into the "Chrome" directory and you'll see 2 example files.
userChrome-example.css
userContent-example.css
Ignore both.. what you want to do is create a brand new file called:
userChrome.css
In this file, put this code:
Code:
@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"); /* set default namespace to XUL */
/* Multi-row bookmarks toolbar */
#bookmarks-ptf {display:block !important;}
#bookmarks-ptf toolbarseparator {display:inline !important;}
/* Sometimes you may need this */
#PersonalToolbar {max-height: none !important;}
/* Multi-row bookmarks toolbar for Fx3b5pre*/
#bookmarksBarContent
{display:block !important;}
.places-toolbar-items
{display:block !important;
height: 65px !important;
overflow-y:auto !important;}
#bookmarksBarContent toolbarseparator
{display:inline !important;}
#bookmarksBarContent .bookmark-item
{visibility: visible !important;}
.chevron {height: 0px !important;}
The line that has "height: 65px !important" can be adjusted to suit your needs. 65 is a rough estimate at doubling it's height but you can have it at 60 or 70 or what ever looks best to you.
Save the file, restart Firefox and presto, your bar is double the size.