maybe fred can chime in here, but lets say If i took a 9.5 inch width wheel with a 49mm offset. the offset is gonna be affected widening it 1 inch, but what would the new offset be?

 

If you added a 1" strip to the backside the new offset is about 62mm.

 

Ditto.... old backspace was about 7.2". New backspace would be 8.2". That would change the offset to 61.7mm (= 1/2" increase). You can't put an 8.2" backspace on a 4th Gen, without a spacer or doing what Keith at ws6.com did when he had his WS6 wheels widened.