Some fellows on a rocket stove forum modeled flue gases, but I can't remember where..... But I do recall they said "free internet based program."
Based on restrictions, the 45°'s will be bettter. A pellet stove flue has an EVL calculation. Which would most likely apply to wood stoves, but with different numbers.. They are as follows... 1' of horizontal pipe is = 1' 1' of vertical is = .5' or 1/2' (because of draft) A 90° is = 5' A 45° is = 2.5' So if you use two 90°'s it's equivalent to 10' (in a pellet stove, but a 90° is still more of a restriction than a 45°)
I was reading the manual on the stove and they stated; in a section outside of the chimney section - which is why I missed it, that the stove requires a chimney 15 feet tall. They did not give any details on where/how you measure the 15 feet.