I am planning to replace the original adjustable GP engine mount on my Reactor 46 (which was causing the whole airplane to vibrate at idle) with a antivibe Dubro Beam mount. I have two questions in this regard as I have never done this before

1) How do you retain the engine centreline with the new mount? The mounting hole dimensions of the original GP and the new Dubro are different

2) How do you actually make the engine mounting holes? Earlier my mentor had set up the airplane for me. I also want to put in either a 75AX or a FS-72A. Both their dimensions are different from the original mount which was carrying a 55AX

Ameyam