Fuel pressure sensor - power/ground alternates for pins 2 & 5

I am about to install a differential fuel pressure sensor for my Rotax 914 on my AF-5500, using the diagram in the installation manual (p145, complete with the 10K resister that came with the sensor.

My first question is this - the pins on the installation manual specify pin 2 (trim power) and pin 5 (carb ground) in addition to the input pin (pin 8). Pin 2 and 5 are already being used by my wiring harness for a trim position sensor (2) and as the ground for the oil pressure sensor (5). Can I use other unused ground and power lines for the power and ground of the differential sensor? For example, I don't have a fuel flow sensor - can I use pin 15 to power the fuel pressure sender instead? Alternately, can I power both my trim sensor and the fuel pressure sensor from pin 2? Can I share pin 5 as the ground for both trim position sensor and the fuel pressure sender? Pin 13 (power) is open but I don't believe I have another ground on the connector.

Do you have an internal engine monitor or an SV-EMS-2XX?

An internal engine monitor supplies 10V to Pin 2 Trim Pwr and to Pin 29 Amp Hall Pwr. So you can either tee the wires together or if the other pin is available just use them. Grounds can be shared as well.

I've got a stock SeaRey 914 setup, so two small boards (71-420 for tach, 71-430 for oil pressure) connected to the 37-pin connector. I'm not sure if that means I have the internal engine monitor or not.

After cross-referencing the pins in use, I settled on pin 30 (amperage #2 ground) and pin 15 (fuel flow sender power), in addition to pin 8. I reconfigured for the UMA sensor and will do some runup tests tomorrow.

Update: My voltmeter and I now understand your comment about only pins 2 and 29 being 10V. I tee