You want to take your throw distance/width (width of original unstretched image) = ratio of compatiblity.
For the most part anything over 1.3 should work with small pincussion effect. In my case with a 13ft throw on my Z2 and 7.57ft width (16:9) gave me around a 1.7 ratio. Another important factor is that you want to place your projector so your using as little of zoom as possible to get your desired screensize. The less zoom you use the less artifacts.
Obviously a longer throw distance would end with a higher ratio, and potentially less distortion, but I can tell you my picture looks very nice and I have very little pincussion at 13ft with my short throw Z2.
