Our current ship is has a "skittish" machine spirit and is xenophilious so we bought a runecaster. One halves warp travel times, the other reduces the time by 1d5 weeks.
How would these combine? And what is the effect of -1d5 weeks on a journey taking merely days?
In our first trip through the warp, the navigator quartered the time, then it was halved again by the runecaster, then reduced by the ships machine spirit. A journey of 60 days was reduced to less than a aday. Can that be right?