The air deflection plates you can buy for most of them help.  Also make sure its not a bar end wistle that's causing harmonics in the roof (sounds like a buzz to me).  End caps on round bars make the difference there.

--
Matt Thyer

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> Date: Sat, 6 Feb 2010 12:02:04 -0800
> From: vanagon@ASTOUND.NET
> Subject: Buzzing luggage rack on westy need advice
> To: vanagon@GERRY.VANAGON.COM
>
> Anybody know a surefire way to keep the luggage rack from "buzzing"?