Reducing servo throw

Right, back on track!
The operating voltages on all the pots and switches is 5volts. The 3 position switches have 3 terminals at the back, to which are connected Ov (Gnd) Open and +5v. When I say open, when I measure with power off, the centre wire measures 550ohms to Gnd and 550 ohms to Vcc(5v) With power on, and switch centre 2.5volts is measured on the centre (signal) connection. With the switch one way +5v is connected to the signal, and the other way Gnd is connected. This is exactly what we would expect. Using a 3 position switch for Channel 9 gives off and on at the servo. Removing the switch and soldering a potentiometer across gives exactly the same movement on the servo.

Now the 2 position switch.
As you can see I've left the switch in and soldered a 4.7k potentiometer across the terminals

What I didn't realise is that the 2 position switch is actualy a change over! One way puts +5v on the signal wire and the other puts Gnd. I only realised this when I turned the pot fully one way and it got rather hot! Luckily no magic smoke!

Then I removed the switch, there are no pull up, or pull down resistors fitted. As you can see from the photo I've soldered the pot in without the switch, when switched on I can vary the signal voltage from 0v to 5v. Starting at 0v the servo is full left, and flips to full right at about 3.5volts. Turning the pot back again the servo flips to full left at about 1.5volts. This would indicate some kind of Schmidt trigger input.
In another life, Analog to Digital converters were very expensive items and came as 1 per chip. When I left the business, chips with 4 A-to-D converters were becoming the norm. It would not surprise me to learn that Futaba only have 8 A-to-D converters on this board.

While I was at it, I linked channel 8 to this switch/pot, and guess what? Yup, when I move the pot the servo moves proportionally! Which I think means that's the end of it. However, all is not lost, Servo city have this and Action electronics have the P96 here
I've ordered the P96 in kit form. (I always buy British where possible)

Klippy - the link you gave takes me to http - and then nothing! You didn't add the url!

Sorry guys, it should be Ok now, there's a minor problem with the link button, if you've copied a link from your Browser, it already has http:// in it, the link button adds another!