Don't know if this is helpful, but RFC 2616 saith:

Due to interoperability problems with HTTP/1.0 proxies discovered since the publication of RFC 2068, caching proxies MUST, gateways MAY, and tunnels MUST NOT upgrade the request to the highest version they support. The proxy/gateway's response to that request MUST be in the same major version as the request.

Also, RFC 2145 clarifies that the minor version the client sends has no relation to the version the server returns. Each should normally send the highest version for which it is at least conditionally compliant.