You can contact Gregg Baker of ISAAC on Rennlist.com . There's a ton of good (and bad) safety info in the threads there as well. Note that much of it may not be applicable to Subies (or most rally cars).

The best source of research is, well, reading the (peer-reviewed) research. Most of the manufacturers have published papers in SAE journals, or made presentations at conferences.

As for SFI, I have little faith in them. They do absolutely zero compliance testing, so as far as I'm concerned, an SFI sticker stands for squat just for that reason. It also seems like if they don't want to pass a manufacturer's H & N restraint - particularly if the manufacturer isn't a member of SFI - then the SFI standard is seemingly revised just enough to exclude that product. Coincidence? ...

As for HANS pricing, everybody has to advertise the same price. Actually paying that price is an entirely different matter ... :-D