Assuming your not going to drill into your new cab...
If you are disrguard the felt recommondation.
Real easy.
1. Take off old rails and take out flipper buttons.
2. Before installing the new rails check to make sure the upper anchor screw fits as it should - if not you can use a slightly larger drill bit to sink it as it should be.
*3.Put a small amount flet on the back of the new rails near the lower edge of the arch so the new art will not be damaged.
4.Put on the new rails using the old rail holes (small screws and upper anchor).
5.The lowest cab anchore hole will have to be chased with a drill bit to line up (trust me on this one).
6. reinstall your flipper buttons.
Terrys rails are great have installed 5 sets getting ready for #6 install.
I agree on the down grade of drilling holes on a new cab hence the felt recommondation.