I usually leave the frog along unless there are little flaps that will catch the dirt and bacteria or in cases of founder, where a frog that's overgrown will cause too much pressure.  Otherwise, I don't touch it.  Lowering the heel will usually allow the frog to be compressed naturally.  If the heel is super high, then you'll probably have to trim excess frog as it will have been attempting to touch the ground the whole time the heels were high.

 

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