I have some and I tried it with NPP. I used the Stallion 200mg Prop and Stallion 200mg NPP. Both are EO based and are very thin. I mixed .5cc of the prop with 1cc of the NPP.
The injection did not hurt any more than my normal 1cc NPP injection. I did this just to try the prop, as it is not in my current cycle. Prop usually kills me, but this was not bad.
If prop usually hurts you and you plan to shoot it alone without mixing it with something painfree - this prop probably wont be any better for you.