Direct inter-vehicle communication enables numerous safety applications like intersection collision warning. Beacons - periodic one-hop link-layer broadcast messages containing, e.g., location, heading, and speed - are the basis for many such applications. For security, current work often requires all messages to be signed and to carry a certificate to ensure integrity and authenticity. However, high beacon frequency of 1 - 10 Hz and dense traffic situations lead to significant communication and computational overhead. In this paper, we propose several mechanisms to significantly reduce this overhead while maintaining a comparable level of security. The general idea is to omit signatures, certificates, or certificate verification in situations where they are not necessarily required. This creates a security-performance trade-off that we analyze in detail. The results show that significant savings can be achieved with only small impact on security.