I am not finding the link in my PM's from Doug but what he did was copy the idea from the Mopar cams where they extended the duration of the exhaust lobe. What it does is makes some difference above 3500 RPM but robs a bit at the lower end. So what Doug was doing was using the RV10 on stock 1 barrels since they are limited by CFM at higher RPM anyway. He then liked RV15's on 2 barrels because they could breath more and the RV15 moved the peak hump up about 1000RPM so you could take advantage of the CFM. The RVP gave you a bit more at the high RPM but took away less at lower RPM than any thing else you could do. For someone like me who takes an engine above 4000RPM once a year, maybe, I would stick with the RV10 for the low. I put oversized valves in which gave me the higher RPM with the RV10 that the RV15 gave without loosing the low RPM. The Dutra Duals with the "Y" behind the transmission crossover with the RV10 (or OC 106) picked up the torque 20 ft-lbs + across the band.
