RE: JR921 Receiver Upgrade
I consider the upgraded "quick connect" feature to be a backup. It should not be the primary means of avoiding a crash. Sort of like an emergency chute. The primary defense against a "brownout" should be a properly sized battery pack and a system that doesn't draw the voltage down too low. The slow blink feature is only good if you can get your plane down without crashing!
Last year I flew precision pattern using an AR7000 receiver on a four-cell nicad battery. Not any indication of failsafe much less a brownout. After that receiver is upgraded, I'll continue to closely monitor the battery performance rather than depending upon the upgrade.
I did have my 921 receiver upgraded. No chance to test it in the air yet. I noticed on the bench, the upgraded remote with the slow blink took longer to bind than previously. If I tried to rebind without a 30-second rest, it wouldn't.
Allan