Designers work in groups. They need to share information either synchronously or asynchronously as they work with parametric modelling software, as with all computer-aided design tools. Receiving information from collaborators while working may intrude on their work and thought processes. Little research exists on how the reception of design updates influences designers in their work. Nor do we know much about designer preferences for collaboration. In this paper, we examine how sharing and receiving design updates affects designersi performances and preferences. We present a system prototype to share changes on demand or in continuous mode while performing design tasks. A pilot study measuring the preferences of nine pairs of designers for different combinations of control modes and design tasks shows statistically significant differences between the task types and control modes. The types of tasks affect the preferences of users to the types of control modes. In an apparent contradiction, user preference of control modes contradicts task performance time.