I fail to see the logic where the leechslot decrease again for the same user, that was granted leech in the same group already?
In this case site change ratio 3 should be disabled to avoid losing slots then..
I haven't tested this, but now gadmin can set ratio 99999999999999? (without loosing any leech slot)
I would rather have a time limited leech slots exchange than disabled..
And at last, it should be possible to configure this behaviour as you please
