Is a 1/2" spacer big enough?

[90TGP]

I know that my factory off-set is 25mm with a 16x8 wheel. The wheels I'm looking at have the smallest available off-set of 40mm on a 17x7 wheel. A 15mm difference which comes out to be 5/8". I was wondering if a 1/2" wheel spacer (4mm shorter) would be adequet enough to place the aftermarket wheel into proper alignment?

Any opinions?

P.S. My stock tire size is 245/50/16. If I went with the 17x7, would it be safe to keep the 245 series tires, or go with a smaller 235 series tires?

Thanks