it's not all that critical. you've got a pretty good bit of leeway with this mod. just try and get it somewhat close to the factory thickness, but don't break your neck trying to get it exact. hell, the factory trigger doesn't fit well anyway--why would you want to copy it?how critical is the thickness of the trigger itself ?
I'm making a new trigger if anyone is curious..
i had to shim my trigger with a washer just to make the trigger wabble bearable; so i'd say you're pretty safe if you make the trigger a little bit thicker.
and for everyone's sake don't lose that ball. talk about a pain. i'm sure you could just replace it with a ball-bearing ball of the same diameter...if you can find one.