Wrong and right tyre sizes but?

[CHIMV8]

Going to change my tyres on 17" wheels all round to Toyes T1Rs.

I do general road driving and very rare do track days.

Currenrly run 215x40 fronts and 245x50 rears.

Is there any reason why i cant change to

205x45 front

then reduce rears back to 225 or 235 x either 40 or 45.

People say the wider the better,but from a ride point of view i'm not so sure.

I know the factory geometry settings were worked out for the chassis etc, but at the end of the day she is generally a weekend run about and does it matter that much.

Help