You have hit on one of the most difficult connection one can do with SIPs. What I would do for the ridge to hip connection is have 1/2" steel plates welded into a "Y" configuration and slot them into the ridge beam and hip beams and then bolt them. One would have to cut access holes in the panels to manuver the bolts and wrench. For the hip to wall connection I would use a single 1/2" steel plate sloted into the hip beam and an internal lumber post at the panel wall corner and bolt. Again one would have to cut access holes for the bolts and wrench. The beams could be made from 2x lumber or engineered lumber.
Jeff;
You are right
the Groover job did not have an internal beam, but the house was over 3000 sq. ft. of hip vault spacethe unsupported hip spans were as much as 32ft. wide with no gusset connections.Actually the project was done by a St. Petersburg architect and it was his first SIP job
The threads do tend to get off course at times, but to get back on track the Hart job was one that had 6" internal hip beams tha spanned 30 ft. with just ridge support