Well my attempt at a double dry hop has failed and has instead become a single dry hop. On day 2 of fermentation I added 3 oz of El Dorado hops at high kreuzen. At that time I also put 2 oz of El Dorado and 2 oz of Bru-1 in a hop sock and, using a magnet, attached it to the inside of the fermenter. It was hard to tell but, the bottom of the bag was either 1 mm above or 1 mm below the top of the kreuzen. I expect it was the latter because 6 hours later the bag had detached from the magnet and was in fully in the beer.
I assume the bag and hops wicked up liquid until they became too heavy for the magnet to hold. Oh well, another lesson learned the hard way. I'll still have beer; it just won't have all the aromatics I was hoping for.