Down wind sails

I just recently bought my first boat with a spinnaker so I don't claim to be an expert on them but it seems to me that spinnakers are not designed to function as a foil. I have noticed that many multihulls have gone from a wide full spinnaker to a much flatter high aspect sail called a Hooter, G-0, or Screacher. These sails look like a huge jib rather than a spinnaker. They have a luff that
is pulled tight and are shaped like a foil, similar to a jib or main. Multihulls have enough speed going down wind to get the relative wind shifted around to 90 degrees or even higher and the wide beam allows the sheeting angle to be much wider
and therefore a much wider sail angle without adversly effecting the sail shape. This brings me around to my question, could monohulls benefit from using a flat high aspect sail down wind if it could be sheeted effectivly at a wide enough angle. I realize this would not be practical but just as an example, if you moved a
bow sprint to the sides of a boat (would that be a beam sprint?) , attach the clew to one and sheeted the tack to the other one on the other side of the boat, so that the sail is basically perpendicular to the direction of travel, would this be more efficient than a spinnaker at a relative wind angle of say 120 degrees? Obviously sailing dead down wind would be faster with a big spinnaker but at what relative wind angle is a foil less effective than just using pure drag to move a boat down wind?