Just a very quick reply as I'm heading out shortly.
That's a bit different from what I expected, which is then confusing relating to the instructions. But the conversion should still be possible. The connections you solder on to on the trainer port circuit board should be able to be traced back to a point on the main circuit board inside the controller, so if you can find them, you should just be able to solder direct to them. The only difference is that you are interrupting the wires at a different point than you would be if you soldered to the trainer board, but that won't have any effect on the functionality of the conversion kit.

It's a Field Force 6 yeah? I'll try and get a picture of the connection points to the main board in my transmitter later on and post it up.