diff --git a/configs/windows/mozconfig b/configs/windows/mozconfig
index 9dc46a804..826eec7dd 100644
--- a/configs/windows/mozconfig
+++ b/configs/windows/mozconfig
@@ -33,12 +33,12 @@ ac_add_options --disable-maintenance-service
 ac_add_options --disable-bits-download
  
 if test "$SURFER_COMPAT" = "true"; then
-  ac_add_options --enable-optimize="-O3 -w"
+  ac_add_options --enable-optimize="-O2 -Qvec -mtune=haswell -march=x86-64 -w"
 
-  export CFLAGS="-mtune=haswell -march=x86-64"
-  export CPPFLAGS="-mtune=haswell -march=x86-64"
-  export CXXFLAGS="-mtune=haswell -march=x86-64"
-  export LDFLAGS="-Wl,-O3"
+  export CFLAGS="-mtune=haswell -march=x86-64 -O2 -Qvec -w"
+  export CPPFLAGS="-mtune=haswell -march=x86-64 -O2 -Qvec -w"
+  export CXXFLAGS="-mtune=haswell -march=x86-64 -O2 -Qvec -w"
+  export LDFLAGS="-Wl,-O2"
   export RUSTFLAGS="-C codegen-units=1 -Ctarget-cpu=x86-64"
 else
   ac_add_options --enable-optimize="-O2 -msse3 -mssse3 -msse4.1 -msse4.2 -mavx -maes -Xclang -w"
diff --git a/src/browser/base/content/zen-styles/zen-browser-container.css b/src/browser/base/content/zen-styles/zen-browser-container.css
index 3b76c89b7..26fd29104 100644
--- a/src/browser/base/content/zen-styles/zen-browser-container.css
+++ b/src/browser/base/content/zen-styles/zen-browser-container.css
@@ -4,8 +4,9 @@
     width: -moz-available;
     margin: 0 var(--zen-element-separation) var(--zen-element-separation) 0;
     box-shadow: 0 0 0 1px var(--zen-colors-border);
-    clip-path: inset(-5px -5px -5px round var(--zen-browser-border-radius));
-    border-radius: var(--zen-browser-border-radius);
+    /* We can't use a border radius here because it brings performance issues,
+    so we use a clip-path instead */
+    clip-path: inset(0% 0 0% 0 round var(--zen-border-radius));
     overflow: hidden;
   }
 }
diff --git a/src/browser/base/content/zen-styles/zen-sidebar.css b/src/browser/base/content/zen-styles/zen-sidebar.css
index 0af94d2b0..5930d16eb 100644
--- a/src/browser/base/content/zen-styles/zen-sidebar.css
+++ b/src/browser/base/content/zen-styles/zen-sidebar.css
@@ -10,7 +10,7 @@
 }
 
 #sidebar-box {
-  --zen-sidebar-box-border-radius: var(--zen-browser-border-radius);  
+  --zen-sidebar-box-border-radius: var(--zen-panel-radius);  
   margin: var(--zen-element-separation);
   border-radius: var(--zen-sidebar-box-border-radius);
   overflow: hidden;
diff --git a/src/browser/base/content/zen-styles/zen-theme.css b/src/browser/base/content/zen-styles/zen-theme.css
index 9f10ab4b6..ac5ca4370 100644
--- a/src/browser/base/content/zen-styles/zen-theme.css
+++ b/src/browser/base/content/zen-styles/zen-theme.css
@@ -89,7 +89,6 @@
 
   --zen-appcontent-border: 1px solid var(--zen-colors-border);
   --zen-panel-radius: var(--zen-border-radius);
-  --zen-browser-border-radius: var(--zen-panel-radius);
 
   --toolbarbutton-border-radius: 6px;