Once comment space fills up for 14, you won't be able to post here and will have to move to past-part fills. I think the reason someone was pushing for 13 to stay in 13 until it was full was to prevent people posting in odd places when there was no need, but if a part is full it's full (15 is open now, anyways).
I'm pretty sure it'd be okay if you start posting in the past-part fills and use the remaining comment space here to post a link to where the story will be continued. I know I'd be upset if you had troubles posting this story or I missed what comes next. :)
I hope I helped...