Don't hide the copyright notice or whatever's at the bottom if you use bottom header.

css/style.css

@@ -93,11 +93,12 @@ a[href="javascript:;"] {
 }
 
 /* Header */
-.fourchan-x body {
+:root.top-header body {
-  -moz-box-sizing: border-box;
-  box-sizing: border-box;
   margin-top: 2em;
 }
+:root.bottom-header body {
+  margin-bottom: 2em;
+}
 .fourchan-x #boardNavDesktop,
 .fourchan-x #navtopright,
 .fourchan-x #boardNavDesktopFoot {
@@ -256,6 +257,10 @@ a[href="javascript:;"] {
 }
 
 /* Settings */
+:root.fourchan-x body {
+  -moz-box-sizing: border-box;
+  box-sizing: border-box;
+}
 #overlay {
   background-color: rgba(0, 0, 0, .5);
   display: -webkit-flex;

src/features.coffee

@@ -146,6 +146,12 @@ Header =
 
   setBarPosition: (bottom) ->
     $.event 'CloseMenu'
+    if bottom
+      $.addClass doc, 'bottom-header'
+      $.rmClass  doc, 'top-header'
+    else
+      $.addClass doc, 'top-header'
+      $.rmClass  doc, 'bottom-header'
     Header.positionToggler.firstElementChild.checked = bottom
     Header.bar.parentNode.className = if bottom
       'bottom'