In my impression, supporting a full stocked Mannlicher under the front king screw (the front action screw), works best for the smallest groups. I'm sure I read that somewhere and it worked for me. I support the forend also just to stop it recoiling out of the rest. But the points made above are good ones and it might pay to also recheck once you have your pet load, that a different hold doesn't change the POI. When I've done this with other rifles, for instance, supported by a large bag stuffed with wood wool, (very long wood shavings), which is sort of like a standing rest, the rifle tested acted the same as on the bench with the same POI in the same place. What will alter things on a thin Mannlicher barrel in an equally thin stock with a stirrup sling mount, is trying to use a tight sling. This will pull the POI off target. You'll still hit the target, but probably left of the exact spot you were aiming at.