I dont have A/C running in my car and I do have a 1 inch spacer and it sits about 80% in and 20% out and I have a new alum 3 core rad with a flow cooler water pump and it runs between 170-190 on 90 degree days with 80-90% humidity. I hadnt heard about the 50 50 thing until this post was started and I started looking into it. While most the looking around the internet seems to agree with keeping 50% of the fan in the shroud and 50% out, I couldnt tell you honestly if it would make a difference as i am happy with the temps I am curently running. I am contemplating pulling off the spacer to see what it does and if I do I will report it back here. Would be interesting to know if anyone has done both and if their temps got any better running the fan half in and half out.