I used to build and fly R/C scale models. In scale, If I were to build from a kit, I would first take photos of all the kit parts, especially any pre-made fiberglass parts. This might show the level of effort required to complete the model, based on the pile of raw materials in the kit. As already noted, any kit represents some level of pre-fabrication,. So the ratio of pre-fab to builder fab is always a subjective issue. Any CD with experience in the event should rule based on both written rules and the most recent trend of interpretation.