POST health check with body XML (Soap)

Help!
1

I want to do a soap request to a server as a health check.

The documentation 2.4, states:

option httpchk <method> <uri> <version>

and

<method>  is the optional HTTP method used with the requests. When not set,
          the "OPTIONS" method is used, as it generally requires low server
          processing and is easy to filter out from the logs. Any method
          may be used, though it is not recommended to invent non-standard
          ones.

<uri>     is the URI referenced in the HTTP requests. It defaults to " / "
          which is accessible by default on almost any server, but may be
          changed to any other URI. Query strings are permitted.

<version> is the optional HTTP version string. It defaults to "HTTP/1.0"
          but some servers might behave incorrectly in HTTP 1.0, so turning
          it to HTTP/1.1 may sometimes help. Note that the Host field is
          mandatory in HTTP/1.1, use "http-check send" directive to add it.

I cant find anthing on how to put the POST body in there.
Is this possible, or is an external check needed?

2

option httpchk documentation also state:

Note : For a while, there was no way to add headers or body in the request used for HTTP health checks. So a workaround was to hide it at the end of the version string with a “\r\n” after the version. It is now deprecated. The directive “http-check send” must be used instead.

http-check send doc:
http://cbonte.github.io/haproxy-dconv/2.4/configuration.html#4.2-http-check%20send