Don, have re-read your book - or at least I speed read it looking for something on telltales and the main but do not see the answer to my question - so here goes.I recently purchased a used main and am currently "playing" with it. Interestingly it came with telltales on both sides of the main at the leech - these are about 6+ inches from the leech so when they are streaming they do not flow past the leech. I have been trying to get these telltales to stream .... but have not had much success so far. - The windward telltales stream but the lee telltales are backwinded/vertical.I have an O'Day 23 - the mainsheet is not on a traveller - it is attached to a triangle plate on the back-stay. The back-stay is not on the centre-line of the boat so getting the boom to the centerline is not possible on a starboard tack.What do you suggest to get the airflow attached to the sail?Also the PO attached some telltales near the luff of the main. Interestingly the lee telltale at the luff is back-winded as well - this seems to say that the airflow in the slot is not very uniform. What do you suggest to improve this condition. I have tried a number of things but nothing has had a major effect yet.ThanksJames