RE: Is this enough engine cooling?
The exit hole can be just about anywhere if the airflow is forced to pass near the engine. It greatly helps to have it directly behind the engine, but if it's at least near that side of the fuselage, it's good.
You also want to have some negative pressure around the exit hole. Most CAPs have an oddly shaped bulge on the bottom rear of the cowling. If you leave the leading edge of that bulge as a "lip" and remove the flat portion of the bulge, the lip will help turn that area into a negative pressure area. Exhaust openings on airplanes very often have deflectors immediately ahead of them to do just that, cause negative pressure downstream.