Phil Ashby wrote:

What I suggested does use an outbound at each end - one pushes the port forward (-L) one pulls (-R)... :)

Oops, misunderstood because of your references to port-forwarding.

I'll investigate further, thanks.

[Phil's email was sent off-list but given its content I've assumed that was an error hence the on-list reply. All of Phil's reply is above.]