First off, what you do to your gun is your buisness, I will hold no liability for any modifications that you do. This is for informational purposes only.
Be sure that when you drill the hole, that you keep it horizontal to the top of the trigger bar, the area that engages the spring is at an angle. Note the red lines that depict this. I uses a meal block in my vise set to this angle and clamped the trigger bar to the block.
You have to keep the hole VERY close to the inner edge of the bar for spring clearance. I used a 4-40 set screw 1/4" long. Be sure to keep it short enough or the magazine will contact the screw when inserted.
Here you can see what I meant by clearance for the trigger return spring. If done inproperly, the spring will not be able to rest naturaly in the correct place on the trigger bar.
Another view of the spring and bar assembly. Notice that I drilled the hole at a slight angle to insure proper spacing for the spring. I do not have any pictures of the process being done, sorry.