Cheers for that. Yes, the trees are 120ft high (and subject to TPO's too, which is a hassle as I own them!). The distance from firing point is actually 47 yards to the base of the most favoured tree. May try the AA Fields, when I zero with Bismags at that range it is almost one hole stuff, amazing. I think you are onto something with the gravity thing.
47 yards to the base of the tree is a fair distance, add in the height and an angle of close to 40degrees, for that with my S200 and AA Fields I would actually be looking at crosshair to 0.5 mildot holdover purely as a ranging shot then che