Tele and Start Bridge installation


Senior member
Okay, Ive now a Tele and a Strat that need bridge installations. There are no previous holes drilled to align. I've figured out how and where  to exactly  place the bridges. I am probably going to order a set of deepthroat clamps to clamp the brides down to mark and drill the bridge screwholes.
Now, the probelm is that when i mark the holes, and then drill,  then screw in the bridges, then  the bridge always  shifts a little, either to the left or right.
I've ruined a previous installation  with the bridge shifting  and had to  dowel the bridge again.
I'm thinking perhaps I should just take the guitars into a professional luthier?
Should I try it again? Im very much a novice at this.