I have a Futaba T8J & Spirit.

Can anyone explain to me how to map rescue to a switch on the Tx?

In Spirit software - General tab - channels - assign F stabi function to either channel 7 or 8
In TX aux channel page assign your rescue switch to the channel you selected

You can test it in the channels tab ( State on or off )

Do you need to set gyro to negative in order for rescue to work?

No, not when you assign a channel for rescue
Negative gyro is the original way of doing it, assigned channel is much easier

I followed your instructions and did it... so happy

I also set the rescue timing to 0.5 secs, which I think gives the heli enough time to ascend and recover properly. The default 0.1 sec is too fast I think.

Will be testing it out this weekend. Hope it all goes well.

Thanks Andy. Couldn't have done it without your help.

The rescue timing (acro delay) is just the delay between activating rescue and flipping skids down using rescue normal. It will level out and climb inverted first if it is nearer that attitude
Rescue acro goes to the nearest attitude i.e skids up or down and stays there
If not using a spring loaded switch the Spirit will stay in rescue mode and keep climbing until you deactivate the switch

Got it