This paper reports preliminary results of an evaluation during which two different bidirectional versions of the limited-domain medical spoken language translator MedSLT were compared in a hospital setting. The more restricted version (V.1) only allows Yes-No answers and short elliptical sentences, while the less restricted version (V.2) allows Yes-No answers, short elliptical sentences and full sentences. Although WER is marginally better for V.1, task performance is marginally worse. There appear to be two main reasons for this disparity; short sentences are often badly recognised and patients tend to find it difficult to limit themselves to ellipsis, even if they receive clear instructions about not using full sentences.