MATE i'm an engineer and do a hell of a lot more when it comes to structures, and cutting that size hole in the car IS F U C K all.
After doing some simple calcs, if at 60 the car was to impact a solid wall, taking the stress and strain modulous of steel and some basic geometry, the differance in the hole there and not there was 0.0045%.
THE HOLE DOES NOTHING FOR THE CARS STRUCTURE. If you hack up the hole they you do introduce a stress point in the car, yess agreed, but the difference is insignificant. TRUST ME.
All an engineer is going to do is tell you to weld a ring arround it to minimise the possability of a stress fracture accuring in that spot. NOW if you ahve a stress fracture that accurs at that point, you have a lot more to worry about as there is more underlying problems with the car.