If you absolutely must splice, (which I don't recommend if you can avoid it) I would skive at least 3" on both sides, and add a liner if possible to strengthen it even more. then glue and stitch. A little hint on skiving long pieces for overlapp, use a belt sander or something similar, it takes some practice to not overdo it, but it works great, you can get a perfect taper up to about 8-10" if you want.