I came to the exact same conclusion!!! I also think it would be best to run the highest offset offered for the front, which is +50mm. So that's what I'm going to order.
On the rear I picked the middle of the road with a +28mm offset. If any adjustments need to be made, the spacer will be very small. Not sure if I will use 2 or 3 inch wider fenders. Thinking about 3 inches, I'm want to tuck the tires about a 1\2 inch under the fender if a use a 18 inch wheel.
Thanks, I just really needed a second opinion to verify my calculations. I feel more comfortabe with making the purchase now.
17x7 et +50mm front
17 or 18 x 9 et +28mm rear
If anyone disagrees, please speak up. All opinions, advice, thoughts, ideas, will be greatly appreciated.