Is it possible to upgrade a springer air rifle? I've heard changing spring size is a no go, is that true? You see my problem is I have a Hatsan mod.55 and 95 but the 55 seems to have lost power since I got it a few months back (its was second hand and I've been using it on a daily basis). The mod.95 is overshadowing the 55 but from what I've read they should perform similarly? What could be done to improve its performance and what can I do to maintain the mod.95 so it doesn't lose its power down the line.