Fast, reliable solution to provide remote control with reverse and direct connection?

Question

I'm looking for the following solution to provide remote support to Windows users:

1. The connection should go directly from the customer's PC ("server") to the support PC ("client"). That rules out options like LogMeIn, CoPilot, TeamViewer, etc.
2. The customer should not have to tweak his firewall to map a port so as to provide inbound access to the support PC. Thus, the server should connect out to the client
3. Once the server-client are connected, the support person should be able to launch Windows' Remote Desktop client, have it connect to 127.0.0.1 so that data goes through the connection established in step #2.

I did try UltraVNC's SingleClick solution, but found RDP to work much better than VNC, which tests showed to be slower, would often freeze for several seconds, the screen looks worse when seen on the client PC, etc.

Does someone know of a solution like the above?

Thank you.