i wouldn't connect the tweeter to your mid. Very bad idea.
if the mid is connected to your head unit, you're going to either drop or raise the impedence on the head unit, and most head units are configured solely for 4 ohm loads. doing this won't instantly damage your unit, but will probably damage it over time resulting in blowing your unit's internal amplifier. your best bet is to wire the tweets to a different channel.
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