For 16 strand, I use a wire fid about 18" long made out of piano wire attached to a retired carabiner. Also, I don't do the bury all at one time. I take it in three stages.
First stage, I bury just enough to get the tapered portion stuffed. When you get to the point where the untapered rope is getting buried, I stop pulling and start snatching at it by attaching a short loop runner into the carabiner allowing me to get a little momentum going before the loop catches creating a little shock load.
Second bury, I go to about 2 inches before the "crossover" area. It goes easy because it's all thin at this point and it's going through straight up hollow cover.
For the third stage, I carefully pretension all the core strands the same amount, then tie the core strands to my ball hitch with a clove hitch. This way, when I start pulling the fid, the cover opens up and allows the final part to go.
I can get a 16 strand splice done in about 30 min and I feel pretty good about that. If I had never climbed on 16 strand and learned to love it before I started splicing, I probably never would have fought to learn to splice it. By far my least favorite rope type to splice.
Hope that helps. It took me a while to get it down, unlike double braid. With double braid, all it took was screwing up 2 splices and after that I've been golden. I failed 4 16 strand splices before I figured out how to use mechanical advantage and about 10 more after that to do it by hand consistently.
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