OK, so we have the mixup about 1C cleared up; your dropping somewhere between 1C and 2C. I personally don't follow the Rao 20% as its kind of complicated, if one uses the other finishing parameters (total roast time, final BT, and roast development time after 1C).
The profile I was referring to (4,3,2,1) charges somewhere 160-180c looking for @ 80-90c turning point (@1:30) then 4kPa till EOD @150c. 160c-3kPa, 170c-2kPa, 180c-1kPa, etc. There are two other profiles talked about, GregR's espresso profile and another that's hot and fast (need to look that one up). The hot and fast profile uses a high ROR to compensate for a shorter total roast time. You can also use a fixed gas setting and make a final adjustment pre-1C around 180-190c.
A normal time to yellow or EOD is 5-6 minutes, 4-5 minute ramp, 1:30 to whatever finish. I think Greg might have a shorter EOD time and longer finish @ 2:30 RD. He also ramps up the heat pre-1C temporarily to increase momentum and cuts the gas at some point coasting to drop.
My opinion, the turning point temperature dictates how much heat it's going to take/time for the first leg to yellow/EOD. Having a consistant TP for the charge weight/profile used helps keeping on track with one's plan.
If you want to extend the time to yellow, try charging at a lower temperature. 160c is only 320f, but you would have to get the Huky lower (if your switching from funnel to pipe) then wait till the BT climbed to the correct temperature.