> Double NAT may cause problems with VPN and visiting secure
> sites with SSL.

Which it does not. I can readily connect from a laptop on the boat, to the
on-boat SSID and it's subnet from the client-mode link to the shore. VPNs
using PPTP, L2TP and IPsec have worked fine. As have several HTTPS
websites, ssh terminal sessions and secured IMAP, SMTP and POP.

Actual experience, not just theory or vendor claptrap, shows it's been
working quite well.

Now, there is the off-chance that the on-shore link won't pass whatever's
necessary for anything other than HTTP traffic. Or is specifically
configured not to pass VPNs. With that being the case it wouldn't matter
how many layers of routing were involved.

-Bill Kearney