BH -
I went through this with my MAY vacation. I slid both APR and MAY vacations in MAR, then the 'decision maker' changed 'her' mind. So, I attempted a second slide with the MAY vacation in APR. Only allowed one slide.
I contacted the Company and the Union. They're both using a 1999 document, and essentially the excuse of "that's the way it's always been". Doesn't matter whether you're in the CIC window and trying to comply with our current CBA - it's all back to the way it's always been. The question neither could answer was - if it's done in the CIC window, who cares how many times we slide. The VTOs aren't built until after that window closes anyway.
Good luck.
Nakazawa