Unladen from my front door, good conditions, and knowing the route well – about 3.5-4 hours to the head of Crummackdale I’d say. No more than about 2 hrs to your spot on Mastiles. Don’t know how relevant that is to you going at a leisurely pace with Bivi gear, but I don’t see it as being a more than a half-dayer.
If you don’t fancy going that far, have a peep at the area around Attermire Scar just east of Settle. There are a lot of springs marked on the map there, and it is a very pretty spot if you tuck yourself away up near Victoria Cave, arrive late, leave early etc. Also allows you to descend Stockdale Lane, which is a fun bonus.