Yes you can. It might help performance but you probably want it more for storm and for a backup to your forestay during stormy
weather. Your stay should be rigged parrallel to your forestay at whatever point you want it to be. You need to have a chainplate attached to a bulkhead or large timber below the point where you tack it down or you need to have a piece of wire or rod
rigging or solid piece of stainless attached to your stem. Once you've picked the point on the deck where you want it then run it parrallel of the forestay to wherever on the
mast. At that point you'll need a substantial fitting (mast hound) that will handle probably 5/16" wire
rigging. If your mast is bendy in the least you'll want to have
running backstays unless the mast hound is near your spreaders where your lowers attach. In a storm you'll put a lot of pressure on that baby stay and you don't want it bending your mast. Contacting a yacht
builder is a very good idea and if that doesn't help then contacting a professional rigger will also help. I'm by no means a rigger but have gone through this mental exercise many times.
kind regards,