We've almost converged Keith!
If lateral static stability is stronger than directional static stability the dominate mode is likely to be Dutch roll. This might however be accompanied by weaker spirally stable or unstable motion. If directional static stability is stronger than lateral static stability, then the dominant mode is likely to be spiral instability. This might however be accompanied by a weaker Dutch roll.
Let me try to summarise what I believe to be the case without using the words
strong/weak or
dominant.
1) The Dutch roll mode is always stable in certified aircraft and is damped with a characteristic time (e.g. time to halve) of a few seconds.
2) The spiral mode can be stable or unstable, and its characteristic time (e.g. time to double if unstable) is much longer than that of the Dutch roll.
3) The coupling coefficients work so that the further along the axis from instability to stability is the spiral mode, the less strongly damped is the Dutch roll mode.
Does that make sense?