Nitrous/Propane injection on Supercharged engine

Hi.

I am currently working on a project to use a nitrous express "wet" kit on a ford lightning (5.4L Roots-blown v-8)

This type of kit pulls fuel off of the fuel rail and mixes it with the right amount of nitrous (adjusted by the jet sizing) to force more air/fuel into the engine.

I have investigated using a second tank filled with propane, so that a ntrous/propane mixture is injected through the nozzle. The advantages of this would be no danger in leaning out injectors near the schrader valve on the fuel rail, the higher octane of propane for preventing detonation, and the cooling effect propane has during its phase change.

I have seen propane/nitrous kits used on dodge vipers, these are sold by BTR.
I have also read about people racing buick grand nationals using propane injection alone to reduce intake temperatures and prevent knock witht he higher octane.

My problem surrounds the tuning of this combination.
The engien managament is controlled by the ECU and using a chip for tuning on a dyno.

What ways would you suggest for selecting jet sizes for the propane, and adjusting for the varible propane/nitrous bottle pressures that will affect the delivery of each one?

Thanks in advance!