Is there a way to do a (302) redirection from the non remap plugin?

I have a remap plugin where this works - by setting he elements of the URL 
and then setting redirect = 1 on the TSRemapRequestInfo object. 

From a standard plugin hooked to the TS_EVENT_HTTP_READ_REQUEST_HDR I
have my two servers being reverse proxied by calling TSUrlHostSet, TSUrlPathSet
and then  

  TSSkipRemappingSet(txnp, 1);
but in some cases I need to issue a redirect request.

I think I need to set the 
   RedirectInfo redirect_info;
in the State struct, in "HttpTransact.h but I can't see how do do this?

Has anyone else tried this?

thanks very much,