As a last resort I have found sit sailing to be quite effective and relatively relaxing. For a SUP sit with your legs out in front of you and hold the wing and sail to shore. If the wind lulls off you can let the tip and end of the strut rest on the water.
I tried it yesterday on a 40 litre board and hanging my legs over the side was quite stable and I was able to sail in. That was more successful than my attempts to wing on a 40 litre board.