Don't let your rotation out upwind. Going upwind in light wind is all about efficiency. Read the first part of this this and set your mast so that it is working properly. Letting out the rotation is just adding drag. With a modern wing mast, rotation is the last place you should look (after cunningham and traveller etc) to changing power it should always be set so the luff tell tails are working. Once moving in really light wind your apparent wind will be a long way forward so if anything you need less rotation not more. Also don't be afraid to actively adjust this setting in the light. When you come out of a tack and have all but stopped the apparent wind will be at or above 45 degrees, as the boat accelerates it will swing forward to around 20-25 degrees so your mast setting will need to be changed to suit.