Kirk,Where did you get that LGV weight stat?LGV was marketed as a 4.2 kg gun. My LGV Master Ultra weighs 4.25 kg, or 9.35 lbs. That's no lightweight, but still a good deal less than the 10.25 lbs you quoted. After 3.5 kg or so, every 100 grams matters. the LGV has such a short barrel and such a long receiver it does not feel all that heavy in the shooting position. Very manageable.
Chris;First of all, thanks for buying a DIANA rifle, especially the AirKing Pro.IMHE, you are using too light a pellet.It MAY be that the gun will settle "down" to shoot that pellet weight accurately, but when you change the spring, you'll be back where you are now.As DT told you, use a heavier pellet and tune the HPM.You will note the difference.HTH, keep us posted!HM