The problem with a rising rate FMU is that you are trying to match a linear increase (striaght line for the fuel) to a curve (boost rate). All you can do is find the best fit. The only way to be sure is to put the car on the dyno and swap out plates or springs until you get the best fit. A dyno with a sniffer will show the AF ratio for each rpm point on the pull so you will be able to look at how it changes and see if you need to increase or decrease the rate.
A programmable system like the Accel DFI or Motec, etc. is the best way to go, especially if you ever want to dial up the boost. I run 18 psi on my car with pump gas with no problem because I have a Motec.
Also, I keep saying this, but be sure you injectors are not so large that you are rich at idle. If you idle rich, you will wash out the rings.