I have no reason to think it won't stay true. I haven't measured, but based on past experience with every other material, it may contract just a tad when your bow is un-strung, especially in a Flemish string. Leaving the bow strung for a little while or take just a few shots will take care of this.
This is the most stable material I've ever used. I haven't tried a low strand count string with it--18 strands is as low as I've gone, even on low draw weights. I haven't found any reason to use less.
Chad