Here are a couple of helpful pages ...
Lots of good shots of rust-prone areas and advice on where to drill drain holes on this page ...
http://www.panteraplace.com/page57.htm
On this page, do a search for 'Rust Proofing' and it will take you to additional shots of where folks add or enlarge drain holes ...
http://www.banzairunnerpantera.com/adventures.htm
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