That's exactly how I had it wired, center leg of RT351. It turned out to be correct, but when I wired it the first time the insulation rubbed off the wire when I reinstalled that part of the chassis and it had grounded out.
It's working!!!!
These pics show the testing and the final product. For power I just wired it right to the on/off. Not sure whether I should add a tiny toggle or not yet. It's not the prettiest mounting, but there's really not a lot of choice here except installing a ribbon cable and connector and making some sort of artsy box for it. But I'm a mechanic, not a woodworker
Things that the instructions don't tell you:
1. For the grounds, you just tie them all together and ground them to the chassis.
2. Compare the positions of the molded dots on the part to the picture in the instructions and make sure you have it correct. The resistor blocks just below and to the right of the LED display have no polarity.
3. Only the wires shown in the photo are needed. The 4 pin connector by the IC isn't used.
You end up with 4 wires coming from inside the radio.....ground, PTT, Tone, and +12V. That's it!! This is an outstanding kit to order because there's no jumpers or guessing your PL frequency or any of that garbage.