Our track is fairly flowing and medium sized. Personally I run a 68 roll out with 58* of timing on an Actinium 13.5. It would be close with an R1 as well. Now, if I am running a D4, the roll out would be between 78-84 typically. Each motor seems to have different characteristics.

The way I set up my roll out with a new motor is to go out with a baseline, say 76 with 42.5mm tires and X pinion. If my car keeps getting faster as my tires get smaller without changing pinion, then that means the roll out is too high (as the roll out obviously decreases with smaller tires). Typically when I have a new motor, I ill keep the pinion the same until I find the "sweet Spot".

With the actiniums we tried 80 as a start and they were dogs, and seemed to get faster as the roll out got smaller. Eventually I settled for 72 and ran like that for a while. One day I started with smaller tires than what I typically would (41.5) and a 72 roll out. That particular day I was lazy and did not change my pinion, and on the 3rd run, the car came alive. I came back and did the math, and the Roll out happened to be at 68. The guys locally that run D4s/TP/Reedy are back more around the conventional 78-84 range.

So the moral to the story is that every motor is different. Add the fact that timing also plays a big role in all of the equation and the answers to do it correctly are several. Much like with AWD's "peaks" analogy ( I call it a bell curve), there are multiple correct ways of doing this and getting good results.