I have a local machine which connects via ssh to a remote machine using a middle machine and a reverse ssh tunnel from remote to middle. Thus both

ssh -J middle:<sshd port> localhost -p <local port>

and

sftp -J middle:<sshd port> -P <local port> localhost

work. What is the syntax for sshfs to use this existing reverse tunnel to mount remote:~ onto local:~/mnt?

I have a local machine which connects via ssh to a remote machine using a middle machine and a reverse ssh tunnel from remote to middle:

remote$ ssh -p <sshd port> -NTR <local port>:localhost:<sshd port> middle

Thus both

local$ ssh -J middle:<sshd port> localhost -p <local port>

and

local$ sftp -J middle:<sshd port> -P <local port> localhost

connect to remote. 

What is the syntax for sshfs to use this existing reverse tunnel to mount remote:~ onto local:~/mnt?