Tire sizes - stock wheels, stock springs

Please give this a chance before moving....

I looked for days through threads with this spring and that wheel - I learned alot, but not anything about 'stock' cars.

I have just a plain 07 CE 4 Auto, steel wheels (16 x 6.5?), and I think/feel the car needs about another inch of tire width, at least in the front. (However, I would only run the same all around for wear rotation.) From past experience, I really like Hydroedge - like another poster buried somewhere in all the spring combo posts.

I would really appreciate knowing the max sizes for matching tires, and then where the limits are (what hits where, and when) - on a stock car. Then, if someone knows, if any simple deviations or mods (lipped?, spacers, cut plastic) resolve the problem. Last, if front/rear differences are worth it, and what the limits would be if they were not matching front/rear.

I would like to stay +/- 3% diameter/circumference, but would listen for width gain. I can do all the math; I just can't try a dozen different sizes. I would really like to add 30mm thread (215 to 245), looks like +15 sidewall to strut is very close - will system flex at top under lateral load? Experience? How about over diameter (tread) to strut - is it dynamically stable?

But overall, this will always be a stock car - spring and wheel wise. It just squeals too much on expressway ramps. (I do load up the rear, trunk, and a hitch - sometimes - but it looks like the strut is the limiting factor.)

Thanks for 'listening' and any replies - I really look at a lot of tire posts for parts modded cars.

THX