The easiest way to mount the motors is to create a template in either Word or Pages, and import a JPEG image drawn from the manufacturer's website. Here I've overlain a circle (in red) of the required diameter (30mm) to match the bolt-holes on the base of each motor, and sized the JPEG overlay to suit.
All that remains to do is to cut these templates out and stick them on the airframe in a way that matches the orientation of each motor. In our case we'll mount the motor with the wires facing the nearest cantilever, with two bolts through the airframe and two through the adjacent bracket: using our template to guide the 3.0mm drill-bit.
(Alternatively you may wish to spend £2500 and upwards on a laser-cutter to make a pattern in carbon-fibre sheet that can be fixed to the airframe, along with the motor.)
You may find that a slightly oversized drill-bit works better for mounting the motor, as the hand-tool is not as accurate as the power-pillar drill few of us have in the garage. In the past I've used a half-millimetre over-size and have yet to experience an in-flight separation of any sort. Use the regular bit first and then adjust whichever bolt-hole(s) are off-centre, rather than use an over-size bit at the outset.
