Since the first post i started to get concerned about leaving my $1500 investment of joy sitting on the top of my car so i have investigated a fin box lock from this site
www.hugedomains.com/domain_profile.cfm?d=boardsecure&e=com;jsessionid=2CD63812E24FDC8368C9A9CB69EC3B76.qscstrfrnt01
it seems to look a lot like the homemade one fester posted .
I ended up emailing the owner of Boardsecure Josh and asked if he would post to Australia ,
he said no problems and quoted me 12.50 us for post to Sydney . that was for the fin lock and cable , so i said sure and then emailed a paypal invoice with a total ... all to easy paid with my credit card and bingo !
i really liked the homemade one but without the necessary metal work ability i found this to be almost exactly the same they also have one that works on the leash plug ... anyway i hope this helps anyone who might be thinking security ....ahhhhhh peace of mind now .
tom