Background: Establishing traceability from requirements documents to downstream artifacts early can be beneficial as it allows engineers to reason about requirements quality (e.g. completeness, consistency, redundancy). However, creating such early traces is difficult if downstream artifacts do not exist yet. Objective: We propose to use domain-specific taxonomies to establish early traceability, raising the value and perceived benefits of trace links so that they are also available at later development phases, e.g. in design, testing or maintenance. Method: We developed a recommender system that suggests trace links from requirements to a domain-specific taxonomy based on a series of heuristics. We designed a controlled experiment to compare industry practitioners' efficiency, accuracy, consistency and confidence with and without support from the recommender. Results: We have piloted the experimental material with seven practitioners. The analysis of self-reported confidence suggests that the trace task itself is very challenging as both control and treatment group report low confidence on correctness and completeness. Conclusions: As a pilot, the experiment was successful since it provided initial feedback on the performance of the recommender, insight on the experimental material and illustrated that the collected data can be meaningfully analysed.