Cutting away the base of the CH pedals is a long and tedious task. Try to get a hold of an electric reciprocating saw if you can, and be very careful during the cut. You have to remove the entire pedal beforehand, or it will get in the way of the cut. If you are also widening the pedal base make sure that both pedals are well supported, perhaps adding small rollers underneath the pantograph arms. In my pedals the drawer slides tend to bend under the weight and catch on the fixing screws if turning while braking fully. I have "fixed" this by filing the slides end stops partially away, but it would have been better if I had arranged for the load to be applied on them sideways.

The way I added the sensors in my joystick means that the original gimbals are untouched by the mod. With a bit of care you can just try one sensor and see if the joystick can handle it properly. All modern joysticks use a voltage divider arrangement, so it really ought to work as a drop in replacement. If you plan to build your own sensors, the 2 magnet approach seems to work the best as Mike pointed out. Hopefully I will have an updated version of that to test soon, using a flux concentrator that should interfere less with the flux between the magnets. That said, it seems to be already strong enough that the hall sensor is saturated at 45 degrees deflection, so I might have to use smaller magnets if I want to get a greater range of movement.