I wonder if it would have been easier to have something like a v-limited lip on the bumper skin first. Then you would have the alumalite attached to the chassis of the car with brackets and the bumper skin along with the v-limited lip will rest on the splitter while attached to the car.
Im thinking of doing it this way with my car... with the possibility of adding some turn buckles attached to my aps "bumper beam" for my fmic.