The question should probably be over in the Products space.
Anyway, you don't have to worry about duplicate data. The autotagged metadata (pointed to by the `gclid` param) will override UTM info on the Google side by default (there's a setting to switch the priority, but you don't want that).
But there's also no reason to use param names starting with "utm_" outside of GA. They have no magic meaning and you could use your own naming convention to completely eliminate confusion.
Thanks for confirming that this won't cause any issues in GA. I haven't considered using a completely different parameter name instead of 'utm'. I may need to play around with that.
Also - I moved this thread to the Product space.