I've had both of mine torn down and tuned already, but I have a major mod in mind that will require pulling the barrel. I never even thought about drilling and tapping for a small screw, great idea!
So Byran, what's next? Although I changed springs on my first one, I was aiming for a more or less stock power level, ended up at 440 fps with JSB Expresses. On the second one, I went with a shorter but heavier spring, it's doing almost 520 with Superdomes. So these things CAN make some power, with the mod I have in mind, I'm hoping/thinking I could see somewhere around 800 fps with medium weight pellets. Just waiting for some addition material to come in, will post more when I've got something, and hope you'll do the same. Later.