Ssh – How to avoid stalled scp transfer when tunneling through a gateway over ssh

I'm try to transfer a large (1GB+) file from one machine to another, but I have to tunnel through a gateway in between. I'm able to transfer small files just fine. However, with the big file, the transfer stalls mid-way through.

After reading a blog post on the stalling scp transfers, I tried using -l 8192 and even tried lowering it to -l 2000, but that just seemed to make it stall sooner:

scp -l 2000 -v -P 2222 username@localhost:/path/to/file.gz .

From the verbose output (-v) of the scp command, it look like the -l isn't getting passed on…

debug1: Sending command: scp -v -f -- /path/to/file.gz

Any other ideas?