The area behind the engine is one of severe turbulance as far as ariflow is concerned. What little additional air entering the fuselage would not have any impact on pressurization in that area. The turbulance is one of the reasons so many people have issues with hot engines. They recognize the need for inlet cooling air but fail to understand the need to direct the incoming to an out going. They end up with a mini tornado roiling around behind the engine, retaining most of the heat they were trying to expel. You can have all the exit area you want, but unless you have provided a means for that expanded air to "know" where it has to go you wasted most of your efforts.

As for any additional air that manages to enter the fuselage, as long as wings and canopy hatches do not pressure seal, and there are pushrod exits, there's not way to pressurize the fuselage.