Issue using control created in VS.net 2003 in VS.net 2002

I have a friend that has an issue using my asp.net C# custom control in Visual Studio.net 2002 that I have compiled under Visual Studio.net 2003.  I never did test it with that version, but I was under the impression that it should still work as long as you don't use any features specific to the 1.1 framework (which I really don't think I did).  My guess now is that this is correct, but only when using 2002 controls in 2003.  I have searched the web, these forums, and MSDN for the last 30 minutes with no real answer.  The guy that runs MetaBuilders (http://www.metabuilders.com/Faq.aspx) tells people to recompile his controls with vs.net 2002.  I'm hoping there is a better answer because I'd hate to maintain separate builds of my control.  Can someone else shed some light on this topic?