Spring relocation without mini tub?

I'm trying to visualize it. The 28x10.5 tires width dimensions are 10" tread width and 12" section. The 28x9 I run now are 8.6" tread and 10.8 section. That would mean the overall width is .6" wider on each side. With 4.5" backspace without spacers the tires should stick out roughly 1/2" further than they do now which is OK. It also lets me get away with not cutting. Is my math off? If I ran the 5.5" backspace then the tires would stick in 1/2" more than they are now. Not sure how that would look.