Thank you for the fine suggestions.
You'll be pleased to hear that the developmental version of the software already adds more adjusted cycle length options: 3/4, 4/3, 1/4, and 4x.
To work around the problem In the meantime, or even thereafter if the actual cycle length is not related to the network-wide cycle length by any of these close harmonic ratios,
- Choose whichever adjusted cycle length is closest to the actual cycle length,
- Set the splits (in seconds) to their correct values,
- Ignore the subsequent warnings about the splits' sum not equaling the cycle length, and
- Set the Vertical Scale on the diagram to show sufficient cycles so even the special-cycled intersections are fully represented in terms of how they relate to the signals with different cycle lengths.
Since ver. 9.0 will include the additional adjusted cycle length options listed above, it will allow mixing 90" and 120" cycles without complaint. All the same, it will obviously not accommodate all possible mixtures of cycle lengths without this workaround. For example, any cycle ratios involving 5 or above (e.g., 1/5, 2/5, 3/5, 4/5, 5/4, 5/3, 5/2, 5x, or anything with yet higher integers) still require this workaround. I'm reluctant to add options involving 5 or greater, as it seems to me that the notion of "coordination" is mostly abandoned when the cycle lengths are related this remotely, and at some point the warnings about the splits' sum not equaling the cycle length can be a useful reminder that this intersection is not in coordination.
Your further comments most welcome.