Um, I had a quick look at mine, the wheel does seem to sit closer to the front than the rear. Although it may just appear that way because they taper off at the back, if you know what I mean. If you want I can take measurements for you. Never seen and XE with 17's before, but no doubt it would look sweet! Currently I am running 225X50X15 but did have 235X50X15 on the front and they rubed on the guards so they had to get liped. Im running 265'sX50's on the back and the car has King superlow springs, so I have no doubt you could fit some nice 17's on there.
I wish it was a V8