I anchor many many times in a place called Culatra Island, here in Portugal.
It has 3 to 5 knot currents twice a day, in both directions.
I have been using the tandem method here, for over 20 years, and never draged once. Do it only one anchor I don't care what anchor.....and bye bye...
I use a smaller Danforth anchor (14kg) with 10 feet of rope, attached to the "head" of my main anchor, a 28Kg plow, then chain, then rope. Here is what everyone uses, or you're dragging all the time.
Works for me, and for the others. Our bottom is mud / sand / weed.
Some say its a disater waiting to happen (specially Craig Smith of Rocna, but he is he, and I am me....,) if the smaller first anchor rolls around the primary as the boat circles with the current. So far in over 20 years no problem what so ever.
I do it.
Here is a drwing