The {cu} is not elidable, it is optional, but leaving it in tends to make a lot of other things elidable.
The reason that {ku} should be elidable (based on the rule) is that there is unambiguously only one place that the required {ku} could occupy.
The phrase {mlatu sisku} can not be a tanru because {noi},{kuho} must enclose a bridi, and {le mlatu sisku ku keha vau} is not a bridi.
That clause no verb.
On Friday, August 26, 2016 at 4:02:51 PM UTC-7, Andrew wrote:
The reason you can't leave out {ku} in {le mlatu ku sisku} is because it is already omitting {cu}. The longest form of this phrase would be {le mlatu ku cu sisku}. Most people pretty much always omit either {ku} or {cu}, but you need at least one between the x1 and the selbri.