"Is it reasonable to assume the doubling of volume (and more) is attributable "mostly" to short covering?"
I would certainly expect that short covering added fuel to the fire but given that the increase on Tuesday was not straight up in an hour but gradual over the whole day I would think we picked up a good portion of new longs as well. My guess would be that after this week we still have 5 million short shares to be covered. We will not know this information, however, until October 21st when the Short interest for the period ending October 15th is released. All said we still have good potential for upside. My bet is that we will hit $15 in the next 30 days.