I would go with 6"-8" for sure and if you are planning to go higher I would go even a little longer for a couple reasons. 1 - you dont want your brake lines to be too short and turn into limiting straps, that just dont work. 2 - if you are thinking of goinging higher, might as well spend a little more now and get some that a little longer than needed, than spend a lot more later when you have to buy a whole new set. It also saves work if you just have to install and bleed new lines once rather than twice. I you get longer ones and they turn out too long you could always coil em and put a zip tie around em or just tie the extra back to the frame.
