Multiple checkouts of a file is possible and advisable in some situations, but you need a good file diff tool to resolve conflicts. Such a tool exist in VSS, but works best with text files (which VCX classes aren't.)

I know there is a tool that create a text file from a VCX to help make the file diff tool work, but it slow down the process and even if you know where are the conflicts, often you can't resolve the conflicts with a simple copy & paste as you would do with a text file.

>VSS is set-up by default to only allow one person to checkout a file at a time, but it can be configured to allow multiple checkouts. The only downside to this is that you'll have to worry about merging changes during check-in (but if people aren't making changes to the same classes like you've said, it shouldn't be too bad). Considering this is how other source control systems like CVS work, I think this is a reasable alternative.
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>Given their existing "source control" system, I think this would still be vastly better.