i've heard stories of getting 1/2 gallon water bottles filling and walking on with it in hand. no questions asked, but they were old people don't know out you. i say try it and see what happens, lol
by now you prolly already made you choice but i got a buddy with the same civic rollin on 19" axis rims and he's ave problems go with the 18's to fill in the fender and you'll be straight