Just logged off Central Station, where I got to with my network adapter through my firewall/gateway Linux box. After installing ipmasq, although the diagnostics went through without problems, connection to Central Station just refused to work, until I applied something I read from LinuxQuestions archives with something else mentioned in PS.com FAQ:s:

jani@ergopro:~$ cat /etc/ipmasq/rules/I00chain.rul
#:
#: **********************************************************
#: *** INPUT CHAIN ***
#: **********************************************************
#:

$IPTABLES -I INPUT -p icmp
$IPTABLES -I INPUT -p tcp --dport 53
$IPTABLES -I INPUT -p tcp --dport 80
$IPTABLES -I INPUT -p tcp --dport 443

After adding the last four lines into the file, I restarted ipmasq so they would be applied:

ergopro:/home/jani# invoke-rc.d ipmasq restart

I haven't the faintest idea if this leaves my box wide open for even the easiest of attacks, so don't try this at home.