The best "wall" maneuver is such that no wing tip drops. You want the plane to rotate to the vertical and just stop there. SOunds like yours is doing this well. Generally a more "tail-heavy" plane will do all the 3d manuevers better than a nose heavy plane. The 18x4W apc prop may be a good combination. I don't have the OS 160. But again in general a flat pitch (low) prop tends to be better for precise hovering (lots of prop wash). Like a helicopter rotor - large diameter and low pitch. I ran a APC 18x6W on my Moki 180. I now have a Moki 210 and am running a APC 20x8 on my profile.
Moving some weight toward the tail may improve the blenders and flat spins. I move the CG rearward until the plane gets hard to fly. One symptom is that the elevator becomes very sensitive. You push the stick forward a little bit and the plane dives down and tends to tuck under. You pull back the stick and the nose pops and tends to stay up. In other words the plane will "hunt" in pitch control. Now you know you have gone far enough.