I installed an 06 mono RTX skid in my RX-1. These are the measurements directly from the 06 RTX which made my installation easy.
The measurements you need are:
Center of driveshaft to center of front hole = 11"
Center of front hole to top of tunnel = 5.5"
Front hole to rear hole = 20.5"
Center of rear hole to top of tunnel = 7.25"
These measurements should get you started, keep in mind, these are the Apex measurements and yours may have differences (like tunnel clearance) so be sure to measure many times and drill once.
Good luck, and have a great riding season.
Otis