Guy Line Length for Superfly Pullouts

I have a new Superfly tarp and Im really liking it so far. Im trying to figure out the best length of guy line to use on the pullouts. It will be covering my BMBH. I dont use hiking poles so they would have to be tied off to trees or a stake which might mean it would take some serious length, but I dont want to go trimming my glowire untill I know whats the most common length people are using.

Thanks

Mine tends to be 12'. I have one tarp where I have two lines to each pullout (4 in total). On another I have aa length of shockcord between the two pull outs a side and a length tied to the middle.