another security question

[augie]

ok lets say i've got an always on connection at home, and i have a 
firewall/gateway between my internal LAN, and the internet.

now suppose i am at school, and i've forgotten a file at home. luckily i have 
my laptop with me, and both my gateway and the machine where the file resides 
are up. what would be the best setup security wise to retrieve my file?

Solution A:
on the laptop in a .ssh/config file tell it when connecting to the gateway to 
use port 30 instead of port 22. thus limiting some direct scans on the 
gateway.
then on the gateway forward all port 30 requests to the internal machine 
which will be running sshd, and will only accept RSA key authentication, no 
passwords.

or

Solution B:
same laptop setup as Solution A, but this time instead of forwarding port 30 
just run sshd on the gateway, and again only accept RSA key authentication.
then from the gateway ssh into the internal machine, again using key 
authentication.

or 

Some other Solution: ...

i have reservations about both methods.
Solution A troubles me because anyone smart enough or lucky enough to just 
try port 30 on the gateway would be let right in to the internal network.
in Solution B i am concerned about keeping private keys on a public machine.

thoughts fellow nblugers?