That splice is not done correctly. I learned 8 plat in the merchant marine years ago, and often, i would be the only man on the ship who could do it, their are two ways, the wrong way, puting two strands under two strands, what you can find with these splices, is they get shorter, untill their is nothing left of them, but, in a sailboat, you wont put enough weight on them to do that. The right way to do it, is split up the eight strands into their pairs, then you take one pair, and instead of puting the two under, like you have done, you put one strand under one, and over the next, then the other strand over that one, and under the next, you work those two strands the full lenghth of the splice, then you start at the next two strands, when you get to the last two strands, it will be so tight, you will have to use a mallot, and a sweedish (hollow spike to get the rope open. You finish the ends, by either by taking the two strands, and whipping them together, or taping them, then you melt the very end with a soldering iron, or heat up an old knife and do it, or if you are really posh, use an electric rope cuter, wich will cut and bond them.