The problem with reusing the same directory is that it becomes infinitely more confusing (and dangerous) deleting unnecessary files that are side-by-side with the new files.
I believe the "solution" to go about this anyway would be to install/import to a new directory until everything's working, then renaming the old directory, then changing the name of the new directory to the old directory, then changing the path info in CP.
I would not recommend that route though, IMHO. I plan on keeping my .Classic install up (read-only) for a while, as I monitor how the redirects are doing. It's not critical to remove the old right away - I think it's actually a good idea to keep it for a while. (And at the very least, I still have Classic running to help answer any Classic questions that may arise...
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