I am in the process of planning stairs from my deck down to a patio. About a 30 inch drop. The problem: I can't take the stairs down at a 90 degree angle to the deck. I need to take them down at up to a 45 degree angle from the side of the deck. so as you walk down off the deck you would be walking slightly to the left as you are going down the stairs. I have started laying down the precut stringers but I am not sure how to judge the length that they should all be.