So the timing is controlled by the ignition system ??
If so, the manufacturer should have provided a spec to phase the rotor to optimize the spark through the rpm range.
Just for the hell of it...
Let's say you have a 4" dia. cap.
Multiply by 3.1416 to get the circumference = 12.56"
divide the circ. by 360 to get inches per degree = .035" per degree
divide the circ. by 8 to get the spacing between posts = 1.57"
Now:
Let's say that at 12 deg initial the rotor is perfectly aligned with the post.
Let's say we want 35 degrees total
This means the system will fire 23 degrees sooner
23 x .035" = .80"
So at full advance the system would fire half way between two posts.
Hmmm !!! Not sure I like a "locked out" system.
The timing degrees are at the crank, only 1/2 at the distributor (0.40), and if you the rotor at around 24 degrees, then the rotor phase is off 0.20 one side at idle, and 0.20 off the other side at 35 degrees, but still the rotor phasing will change when a computer is adjusting timing with a locked distributor.
The Full advance swing (excluding vacuum advance) of 23 degrees crank or 11.5 (just make it 24/12 to make the math easier) distributor. Split the rotor rotor phasing so worst case, the rotor is off center by about 6 degrees off either way from the cap terminal (the 0.200").
With the locked dist and computer controlled timing, you want the rotor phase to be aligned with the cap terminal just a bit before total advance WOT (no vacuum advance.)
This puts the majority of the rotor closer the the terminal from idle to Max RPM under WOT. At the vacuum advance, higher timing, the rotor can be slightly more offset.
With modern ignition systems, the cap/rotor relationship is a limitation. That is why you only get multiple sparks from a MSD from idle to around 3,000 RPM.
Most new cars use coil on plug, or coil near plug, and eliminate the cap/rotor distribution problem.