This has been discussed before. The RIO is a pain if the operator is not used to it but it is there for safety. Disengage the blades before backing up and leave the RIO alone. Just my $.02 (Cdn)

I don't own an X300, but I have an L111 which may be similar in execution. The reverse sensing switch is not on the deck. It is on the top of the transmission on the right hand side. You can follow the engagement linkage from the foot pedal back to the transmission. There is an electrical switch that gets depressed by the linkage when the reverse pedal is pressed.
On the L111, if you disconnect the electrical connector that goes to the reverse sensing switch on top of the transmission, the RIO button is no longer required to press to mow in reverse, because the electrical signals now never tell the tractor's safety system that reverse is engaged.

I bought a X300 at the start of the summer. It is there, you have to really look hard for it. It is next to the forward foot control on the top of the frame. You will need a 10mm socket to remove it. I removed it, tie-wrapped it closed, then tie-wrapped it to the frame. I also removed the park brake switch. Drilled a hole in the dash next to the key. Mounted the switch next to the key. You have to push the switch in to start, then release it. It's nice though, you don't have to engage the brake to start the mower. Both "fixes" are done so that I can put them back to "factory" if needed. You would want to do that if you have to bring the mower in for service. If you don't the dealer will do it for you.

Thanks mark59, I will give it another look! The RIO is the only safety feature that irritates me, I can live with the others.

This blog needed an update so here it is. I hate the RIO. It slows me down, very inconvenient. I am 58 years old, been driving since age 14 and accident free-- I can handle the reverse mode on my mower at all of 5mph. The RIO indeed can be easily deactivated by using a 10mm wrench on the the bolt that holds the electric switch in place. Very awkward to reach it, but can be done. Located under the frame on the gas peddle side of the mower. Simply use screw driver to dislocate the switch out of the way after the bolt removed, not necessary to tie it to anything, it stays put. Then sweet freedom from one of life's annoyances. Happy mowing.

I'm new to this site and was benefited from the information you folks posted. I'd like to give back by posting as few picture showing the location of the RIO switch. I needed to make an adjustment! Many thanks for your help....

2nd attempt to upload!

Look under the tractor and follow the forward/reverse linkage to the transmission. When you press reverse a pressure switch is depressed. Simply unplug the pressure switch located at the right hand side of the top of the transmission. This will solve the problem without any cutting of wires on any model. How is pressing a button instead of looking behind you safer?

I too have a X300. If the unit came with a key and John Deere tag,,, lift the RIP lever and slide the JD tag under the engage lever holding it up and you can cut in reverse.