Im more confused than i was before now
I have set the gear switch for GPS and Failsafe now but I'd like it to just go to failsafe when Tx lost rather than having a switch (I dont see why you would need to manually switch to failsafe if you still have comms to the Rx). I dont see any failsafe option on the Tx and I don't really know how to setup another switch to do the U input thing you suggest.
thurcombe, sorry for confusing you. I'll try to explain myself a bit more.
There are multiple ways to get the Naza into Failsafe mode.
1. The easiest way is using the Naza Software Assistant, you can configure the U channel to be GPS, ATT, FS, and giveup usage of MANual mode. I personally do not like this because I want Manual mode available if I need it.
2. Setup the Naza for the U channel to be GPS, ATT, MAN, but then have the transmitter send a value (based on a switch) for the U channel to be in between those three mode into the region called Failsafe. This is something external to the Naza, and requires special programming in the transmitter. Sadly, I do not know the DX6i transmitter, so I can't help there, but I would search YouTube; that's where I found out how to do that for my Futaba. Basically you are going to do a "mix" of two switches. One three-way switch that commands max, middle, min values which associates the three positions to the three flight modes. Then you "mix" in another switch which adjusts that same output of the 3-way switch to force a value in the in-between area. This way you can trigger the Naza into Failsafe with this other two position switch.
The above two methods are the pilot triggered ways of getting the Naza into Failsafe, and it is advisable that you setup one of those two. However, there is the true Failsafe intent which is the case when communication between you and the Naza is somehow broken, typically because the receiver is no longer receiving the signal from the transmitter. That is the transmitter/receiver failsafe programming that everyone should also setup. If this is setup correctly, the Naza failsafe will kickin if power is lost to the transmitter, or the signal is lost because you flew out of range. Again, I don't know the DX6i, so I can't give you specifics. But the jist is that you program each of the outputs to a specified response if communication is lost. So on my Futaba I have the throttle output set to 25% if the signal is lost, and the U channel set to a value that puts the Flight Mode into the Failsafe region.
So all of the above settings/programming should be verified on the ground with the Naza Software Assistant running to confirm the Naza flight mode is truly "Failsafe". Then, once you have confirmed that, try invoking Failsafe with one of the switched methods. Once you have confirmed stuff and you feel confident, then maybe you can try the loss of power method, but just be careful. I have tested it that way, and as soon as I confirmed it was returning back home, I turned it back on just to give me that piece of mind.
As to another question you had earlier... "Intelligent" shutdown is what I prefer, so you're fine there. I was just wondering why your MR just fell to the ground, and I'm guessing the Naza is getting a zero throttle input when you power off your transmitter. You can double check that with your Software Assistant.