Just looking how thick arrows are and making assumptions on the bow poundage might be deceiving. Look at standard Ottoman war arrows, which might be 0.8-0.9cm thick and 70cm long. But bows were 100lbs+
Archaeological evidence? Evidence is in the Topkapi and Military Museum in Istanbul. Just read Adam Karpowicz's book.
More texts which give us clues: http://atarn.org/islamic/persian.htm
G?kmen