About tire stretching.. is half an inch (0.5 in.) OK? 175/65R15 on a 15X6.5 wheel

This is a 2012 Honda Fit (base model)

It comes with steel wheels in the size 15x5.5 with 175/65R15 tires, the wheel offset is 53mm.
The wheels are 18 lbs, the tires Sumitomo P02 tires are 18 lbs. for a total of 36 lbs.

It is being replaced with 15x6.5 Konig Heliums with a +40mm offset, these wheels weigh 11 lbs. with lighter weight (but still quality tires,) I can save about 10 to 11 lbs. per corner of unsprung weight.

I’m guess people are voting no on this, an alternative size for these new wheels are 185/60R15. Maybe that’s a better size.