In a post a little while back in the "Braid, diameters,testedBS & buy guide" thread I said I was using a lot of Berkeley's X9 braid lately. A bit more time & use has produced some issues with the X9 construction that significantly affect its casting performance. The X9 construction is a fairly typical x8 construction around an added central core making 9 carriers total. When new & lightly used the line is smooth, round, casts well, diameter is slightly larger than comparable X8 braids like Jx8 etc & casting distance was only slightly less because of that, it had good abrasion resistance. With more use & fighting some pretty large fish on drag settings above 60% of line BS the central core is creeping inside the 8 carrier outer braid & is being forced outside the outerbraid in loops..............in the two samples I have experienced the loops vary from 12" to 30" apart, are repetitive throughout the section of line out between angler & fish during the fight , & loops vary up to nearly 1/4" in length. this is affecting the casting significantly & has led to an increase in loop pickups & guidewraps.... I am pretty sure it has also reduced BS by somewhere around 10% I wondered , before buying some, what the central core would do under tension as it appeared straight down the centre with the 8 carrier braid wrapping at a high angle around it. I'm prepared to try new stuff, but my concern was that the X9 construction would place more tension when under load onto the centre core than the strands in the 8x braid & both load & stretch would be differential . Would the centre core be the same material as the outer 8x braid strands or be something that might stretch a little more than the outer braid strands to loadshare with the outer braid & how would that perform with the fingercuff pressure from the outer braid.. No info on material details has been provided by the manufacturer ( and not expected). The centre core certainly keeps the line nice & round when new & lightly used , but has a downside far worse than any benefits gained from the centre core. This braid is now on my "No Buy" list due to the loops of the centre core forming. now trying some of the new generation FirelineX8 to see if that has improved on the "Exceed" variant. Passing on my experiences for others to consider & comment.