Man, I've go to get a chrony. I modded my Disco in a similar way, however I used a hollow brass insert as a spring guide. The hollow brass insert still allows the degassing tool to work, with the hole small enough to use the adjusting screw effectively. I should add, that I tore down my Disco after firing about 650 shots and found that the factory spring was slightly arched and bent on one end. As well it measured about 3/16" shorter than the new one I ordered from Crosman. With the new spring and power adjuster, I find a noticeable improvement, however, I also find that I have fewer shots per fill. But being cold as it is here, it's no wonder I have less shots.
-Shel