@ShugMan, Sprinter / Raider is best with the stock sizes both front and rear. The reason for rear is already mentioned by our fellow @ammarzahid. For front the handle movement will be felt little jam but you may try. I asked the same from my mechanic and he did not recommend it.
BTW, you should go for 1.6 * 18 rear rim, it will add more road grip. I consider myself very lucky that I got mint condition original Japanese (used ones) Takasago rims both front and rear 1.4* 18 front and 1.6*18 rear and since then no need of rim alignment. I have installed them more than 1.5 years ago and its peace, no puncture issue, no rust also.