I think the most important thing is that the strings should clear the back of the bridge as they slope down to the holes.

Also you might want to search about how best to drill the holes especially if you're going for the straight line lay out.

I think the main problem seems to be the drill bit flexing & lots of people get the layout, drill 1/2 way through except for the two end holes, then drill the other 1/2 way through from the back. There are templates - jig designs about too.