I have no reciprocity data for FP4+, only anecdotal observations.
This has quickly become one of my favorites for nighttime photography. I prefer it in Diafine for that usage.
The maker of Diafine suggests an EI of 250 for use with FP4+. Instead, for nighttime use I halve that and rely on my F3HP's AE mode to establish a baseline exposure. I also estimate exposure based on the EV for a given scene (metered when possible, estimated otherwise). From there I'll bracket in full stops one up and one down.
So far this has given me at least one and usually more than one usable exposure. I simply treat the lighter or darker exposures as different interpretations of the scene.
For 35mm or rollfilm use I believe this is a viable method if you have enough time. If you're using sheet film or time is short and you can't bracket, by all means you'd want the reciprocity data.