diff --git a/build_library/release_util.sh b/build_library/release_util.sh
index c36ad0101d..cbd75476fb 100644
--- a/build_library/release_util.sh
+++ b/build_library/release_util.sh
@@ -4,6 +4,7 @@
 
 GSUTIL_OPTS=
 UPLOAD_ROOT="gs://storage.core-os.net/coreos"
+UPLOAD_PATH=
 UPLOAD_DEFAULT=${FLAGS_FALSE}
 if [[ ${COREOS_OFFICIAL:-0} -eq 1 ]]; then
   UPLOAD_DEFAULT=${FLAGS_TRUE}
@@ -16,6 +17,8 @@ DEFINE_boolean parallel ${FLAGS_TRUE} \
   "Enable parallelism in gsutil."
 DEFINE_boolean upload ${UPLOAD_DEFAULT} \
   "Upload all packages/images via gsutil."
+DEFINE_string upload_path "" \
+  "Upload files to an alternative location. Must be a full gs:// URL."
 
 check_gsutil_opts() {
     [[ ${FLAGS_upload} -eq ${FLAGS_TRUE} ]] || return 0
@@ -24,6 +27,11 @@ check_gsutil_opts() {
         GSUTIL_OPTS="-m"
     fi
 
+    if [[ -n "${FLAGS_upload_path}" ]]; then
+        # Make sure the path doesn't end with a slash
+        UPLOAD_PATH="${FLAGS_upload_path%%/}"
+    fi
+
     if [[ ! -f "$HOME/.boto" ]]; then
         die_notrace "Please run gsutil config to create ~/.boto"
     fi
@@ -34,9 +42,10 @@ upload_packages() {
     [[ -n "${BOARD}" ]] || die "board_options.sh must be sourced first"
 
     local BOARD_PACKAGES="${1:-"${BOARD_ROOT}/packages"}"
-    local UPLOAD_PATH="${UPLOAD_ROOT}/${BOARD}/${COREOS_VERSION_STRING}/pkgs/"
+    : ${UPLOAD_PATH:="${UPLOAD_ROOT}/${BOARD}/${COREOS_VERSION_STRING}"}
+
     info "Uploading packages"
-    gsutil ${GSUTIL_OPTS} cp -R "${BOARD_PACKAGES}"/* "${UPLOAD_PATH}"
+    gsutil ${GSUTIL_OPTS} cp -R "${BOARD_PACKAGES}"/* "${UPLOAD_PATH}/pkgs/"
 }
 
 make_digests() {
@@ -57,7 +66,7 @@ upload_image() {
     [[ -n "${BOARD}" ]] || die "board_options.sh must be sourced first"
 
     local BUILT_IMAGE="$1"
-    local UPLOAD_PATH="${UPLOAD_ROOT}/${BOARD}/${COREOS_VERSION_STRING}/"
+    : ${UPLOAD_PATH:="${UPLOAD_ROOT}/${BOARD}/${COREOS_VERSION_STRING}"}
 
     if [[ ! -f "${BUILT_IMAGE}" ]]; then
         die "Image '${BUILT_IMAGE}' does not exist!"
@@ -76,5 +85,5 @@ upload_image() {
 
     info "Uploading ${BUILT_IMAGE##*/}"
     gsutil ${GSUTIL_OPTS} cp "${BUILT_IMAGE}" \
-        "${BUILT_IMAGE}.DIGESTS" "${UPLOAD_PATH}"
+        "${BUILT_IMAGE}.DIGESTS" "${UPLOAD_PATH}/"
 }
diff --git a/lib/catalyst_sdk_stage4.sh b/lib/catalyst_sdk_stage4.sh
index 4d264498b4..44ad54587f 100644
--- a/lib/catalyst_sdk_stage4.sh
+++ b/lib/catalyst_sdk_stage4.sh
@@ -3,32 +3,28 @@
 source /tmp/chroot-functions.sh
 
 # Build cross toolchains
-# crossdev only does full bootstraps so if all of the packages are already
-# installed (i.e. we are updating an existing stage4) then use emerge
 for cross_chost in x86_64-cros-linux-gnu; do
     echo "Installing toolchain for ${cross_chost}"
     cross_pkgs=( cross-${cross_chost}/{binutils,gcc,gdb,glibc,linux-headers} )
-    cross_bootstrap=0
-    for pkg in "${cross_pkgs[@]}"; do
-        if ! portageq match / "$pkg" | grep .; then
-            cross_bootstrap=1
-            break
-        fi
-    done
+    crossdev --ov-output "/usr/local/portage/crossdev" \
+        --env 'FEATURES=splitdebug' \
+        --stable --ex-gdb --init-target \
+        --target "${cross_chost}" || exit 1
 
-    if [[ "${cross_bootstrap}" -eq 1 ]]; then
+    # If PKGCACHE is enabled check to see if binary packages are available
+    # or (due to --noreplace) the packages are already installed. If so then
+    # we don't need to perform a full bootstrap and just call emerge instead.
+    if [[ -n "${clst_PKGCACHE}" ]] && \
+        emerge ${clst_myemergeopts} --usepkgonly --binpkg-respect-use=y \
+            --noreplace "${cross_pkgs[@]}" &>/dev/null
+    then
+        run_merge -u "${cross_pkgs[@]}"
+    else
         crossdev --ov-output "/usr/local/portage/crossdev" \
             --portage "${clst_myemergeopts}" \
             --env 'FEATURES=splitdebug' \
             --stable --ex-gdb --stage4 \
             --target "${cross_chost}" || exit 1
-    else
-        # Still run --init-target to ensure config is correct
-        crossdev --ov-output "/usr/local/portage/crossdev" \
-            --env 'FEATURES=splitdebug' \
-            --stable --ex-gdb --init-target \
-            --target "${cross_chost}" || exit 1
-        run_merge -u "${cross_pkgs[@]}"
     fi
 done