Blade 400 and new servos

[dam74]

Have bought some new servos for my Blade 400, nothing flash just some D12-MG by AcerLab. Some guys have tried them out and apparently given them the thumbs up according to the owner of the hobby shop I use.
I've installed them but haven't put the ball heads joint in the servo horn that came with the servos as the thread don't fit in the hole.

Should I vice drill them out to size, tap them out or thread them through with a bit of force?

[Mart61]

How much too small are they? I've always screwed mine in with a little force and used the nut on the back too, with some threadlock of course.

[dam74]

They come with four horns/arms. A wheel, arm, double ended-arm and what looks like a cross (not sure if they have proper names). The arm and the cross has smaller holes then the other two. The other two have holes that are very close to the size.