Tim,
Stein make some good points.
One thing to think about is putting those penetrations close to the engine mount tubes so you can use them to support the wires with adel clamps.
Just make sure you don't put those holes over the battery or anything else there for that matter. Later on you might not be able to get the battery out.
Here is a picture of where I ran mine and how I supported the wires. The black tube is the vacuum lines for my dual P-mags.
BTW, I have a Dynon D10 EMS mounted on the right side, centered in front of the passenger's seat.
__________________
Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html