Board Thread:Fleet's Prepared-ness/@comment-26316660-20150714031102/@comment-26289480-20150714125432

so far reading from chinese sources ( I am chinese background)

15.5 cm on CL does have FP bonus

but it is not enough to make up the gap b/w 15.5 cm to 20.3  cm.

So it is not worth it. There is no penalty for CL using 20.3 cm. (just bonus for 15.5 which is not enough)