Hi,
I guess you are talking about the PX45 Chassis, Item number tt-ch045-15s.
On the product page you can download a pdf file , which is the datasheet of the chassis. Scale is 1:1, so you can e.g. import it into inkscape and measure all cutouts you want.
For the PX45 and the other amps which are using this chassis we use the 16 mm alpha potentiometers, so the drills will fit if you use this potentiometers. If you want to use an other kind of potentiometer you must enlarge the drill by yourself.
This chassis is not designed to be a common JTM45 chassis, it is designed for your kits and products.
Best regards, Dirk