I would like to setup my BM to be a Cache Hierachy Client. I would also
like it to bypass the Upstream server if it is down.

There is an option when configuring "Cache Hierachey Client" that is
"Must Only Forward Through Hierachy" although the help on it is a bit

"Must Only Forward Through Hierarchy

If this parameter is enabled, the proxy must pass through a Web cache
hierarchy to retrieve a requested object. Otherwise, the Web hierarchy is
not used, and the proxy retrieves the requested object directly from the
origin server."

If I leave this option disabled will it then use the upstream proxy server
unless it is unreachable?