HI Tigerpies
Ok I will assume noob status
First up of all the radios and modes you have chosen the combination least used with the RC5HL. There is a setup thread for the Spektrum here:See the Setup for MODE 2 operation diagram for channel order. You seem to have got CH5 worked out if you can turn on the tank.
Now my usual on Spektrum radios - these radios are great for flying thingies that don't reverse. Planes don't reverse so everything about the Spektrum radios bears this in mind. Spektrum radios do not have self-centering on the throttle lever. My first guess is that you are starting the tank with the throttle lever at the bottom to avoid any throttle warnings from the radio.
When you start the tank the throttle lever must be at centre so that up stick is forward and down stick is backwards. Because it is not self centering you will have to set the lever manually each time at startup.
If the stick is at the bottom when the RC5HL calibrates it will see the entire stick movement as forwards only.
Good luck
KG