Now I'm going to try and explain the lock stitch i use for this. First I pull off a very long length of artificial sinew. Artificial sinew is cheap so don't get stingy. It's far better to waste some than to come up short half through a series of stitches. I use two glovers needles for this type of stitch. I thread both needles onto this thread and tie it off so I have a loop with two needles. The knot is the positioned so that when I pull the loop tight with a needle at each end, one needle is twice as far from the knot as the other needle or in other words the knot is one third the length of the loop from one of the needles. Be sure to double knot the artificial sinew as it's slick and doesn't hold a knot well. Now remove one of your temporary stitches and starting at that hole and from the inside, push the needle with the longest part of the thread through until the knot stops it from going further. Now run the needle into the next hole and pull the thread back in until it pulls tight. The short piece of thread doesn't ever get poked through the seam. The long thread loops around the short thread and the needle is pushed back through the same hole that it you just pushed it into. When pulled tight, the stitch will be nice and secure. Then move to the next hole, push the needle through to the inside, loop around the short string inside, and back out the same hole. Pull both threads tight and repeat. Terrible explanation I know, but it's the best I can do. Once you get to last hole, run the needle in to the inside and tie it off to the inside thread. Be sure to double knot.