The longer tri-wing bolt won't fit properly into the new battery I got through ifixit. The hole is too small and appears the wrong shape. It seems like this was the case with the old battery too, as there a crack in the corner near the hole where someone had to widen it. In the end I used the tip of a metal knitting needle (the sturdiest thing of the right size I had to hand) to widen the hole slightly, causing a similar crack. I guess since the bolt's thread is only at the tip where it enters the metal laptop casing this shouldn't affect how securely the battery is joined.
I had no joy with a 00 Phillips either, but this was probably due to the crappy quality of my socket set.