Ron,

RaceQs uses the B factor of 550 so, 650/(PHRF +550) . The factor of 550 is recommended by US sailing association for all average conditions and used by  vast majority of the regattas.  http://www.ussailing.org/racing/offshore-big-boats/phrf/time-on-time-scoring/

We will consider adding the setting for changing PHRF factors in our later release.