Have you considered having them x-rayed?
Here's a couple of links.
The American Society for Nondestructive Testing
http://www.asnt.org/
The following is quoted from this article.
http://www.irwinyachts.com/Drawings-...hainplates.pdf
"In February 2003,
Trinidad Inspection Services Ltd.
charged me US$130--six shots at
$21.66 per shot."