I have now got three of the Planet RM6 receivers and it appears that there are two versions of the failsafe firmware.
The two boards with a date code 2409 (week 24 2009) have the system previously described but one board with an older code 0409 (week 4 2009) has a fixed failsafe which sets the output pulse to about 0.8ms for 1 to 2 secs before stopping the pulses. This is OK unless you have the channel reversed then it gives the servo fully in the other direction. I think most speed controllers are off with short pulses so they should failsafe. I don't know how many of these are out there I just got mine from Sussex Models but it is worth just checking how your failsafe works. I have emailed the distributors to try and confirm this and will let you know if I hear back.