I never mess with tillering trees much, I rough to bow dimensions and bend it over my knee to feel which limb is stronger, and see what areas are already stiff or weak, then I put on a long string and head to the mirror and flex the limbs to see where the stiff or weak spots are. I then progress from there with the rest of the tillering process. I like this method as I know how the bow will feel in my hand very early on and can make adjustments for comfort or twist that I wouldn't see otherwise. (also i'm to lazy to make a tree).