Hi taximart,
You could probably use one of my favourite tools, the router, to non-destructively route around the thicker parts to produce an exact copy without the pesky margin which usually results from tracing round...beware though that the router is a potentially lethal power tool which, as it needs some controlling side pressure to hold its rapidly spinning pilot bit against the original part, might only be suitabe for copying flat panels thicker than 2-3mm, though if anyone has safely and successfully routed round stuff much thinner please tell us all how its done...good luck with the build of a cracking boat!
Regards,
Andy