So, at 4,000 CFM and 70,000 BTUH gain, you gotta bring in air from outdoors that is 16 degrees cooler than 110^F, or 94^F. Wow. Once the temp goes above 95, you either increase airflow or attic temp creeps over 110.
At 1,500 CFM, a common rating for a PAV, to hold 110^F in an attic at 70,000 BTUH gain would require make-up air that is 44 degrees below 110,^F or 66 degrees, to keep the attic at 110.
So...with typical summer conditions, the best one can hope for by forced ventilation is to cool an attic off from, say, 130 - 140 to 110 - 120. That's not bad, but we're still not at the ideal state of an attic being as near to ambient as possible. With RB and good natural ventilation, it might be an equivalent reduction vs. a non RB attic with a PAV. The difference being the passive solutions don't draw conditioned air from the house at the same rate a PAV would.
It seems to keep coming back to my earlier bullet points...do all of it, and the solar PAV seems a viable option if the ceiling adjoining an attic is well sealed. I would LOVE to see study data that reflects such an approach, as to how effective it might be.