Barbar Ripple Cushion - Seaming Crochet Edges

I finished Marco Baby's cushion cover which was a test run for making him a single bed size ripple blanket  using a poster of Babar and the Elephant as the colour inspiration. I wanted to make sure I was really happy with the colour combination and stripe configuration before embarking on such a massive project. I'm glad I did because although I love the way the cushion turned out I decided I didn't like the amount of yellow, so for the blanket, which I have already started (see image below), I'm going to swap around the green and the yellow stripes and also make the wide stripes one row wider as I think this will look better for the larger blanket.

Generally I am not scared of seaming. I really don't mind seaming knitting but I am less keen when it comes to crochet, especially when I have to seam the sides of double crochet stitches because I have yet to find a truly neat and satisfying method. When I came to seam this cushion I wondered if using a sewing machine with normal sewing thread might work. It occurred to me that using a straight stitch could be very tricky because you'd have to match up and sew downwards through the centre of the dc posts and ch3s both sides simultaneously. Even if I carefully tacked the edges I foresaw that I would "miss" and have holes and gaps. I wondered if a wide zigzag stitch would work better? More chance of catching everything in? Well, it didn't quite work out. As you can see from the image below, some of the stitches are clearly visible. However, where it did match up properly the result was almost invisible.

But this gave me the idea of using normal Guterman polyester sewing thread to hand sew the seams with a whip stitch (with fabric wrong sides facing), going through the centre of each stitch post and ch3 with at least 3 small stitches per dc. Looking at the picture below, the seam is almost invisible, neat and strong. It's also less bulky than using the DK cotton thread of the cushion to seam with. I am really happy with this and will be experimenting using this method when seaming clothing as the reduced bulk in the seam will have a definite advantage.

How do you usually seam crochet? If you have a preferred technique or method, I'd love to hear about it!