sounds reasonable. i would recommend to use instead of the nested if a multi-line if condition to make the intention clearer, to use non-numeric comparison operators to avoid surprises .. and the X-SSL-Request part is truncated, maybe a cut&paste problem.
An open issue is the secure port, if this is not 443. One needs probably the SystemURL kernel parameter in the proxy cases to contain the https://host:port, so why not use this?
