well, there is little if any vibration in a turbine model, so that being said you could probably get away without using grommets. flight induced vibration (harmonics) may be another thing to consider. no real data to confirm how high those levels are yet. also finding a suitable fastener to take the slop out the now oversized servo mounting hole (without a grommet) will also be something to consider. you definetely dont want any chance of servo movement. i would use them.(grommets)