After looking at the front. It needs either the space between the lower fairing and the headlights filled in with body work. Or the wheels need to be moved out of under the in a more open wheel style with a fender placed over them. Either show the wheels or cover them up from the front. Don't try to do both.
revisiting the back of the slingshot. There is just too much space between thTween tire and the bottom of the body. I know there are some mechanical pieces that are not shown in this rendering like shocks, drive belt or shaft, fender or mud guard over wheel. But I am afraid it is still going to look bad. A wider tire and some body work to close the gap would fix the something missing. Like it was suggested in a earlier post maybe add some storage on the sides to close the gap.