Tricks of the Trade - Arrowhead Tacks

While remaking the Turquoise Tartan skirt, I found the stitching on the back inverted pleat had started coming undone slightly:

I thought I'd give one of those arrowhead tacks a go.  I have to admit I haven't done these very often and had to refer to my old Vogue Sewing book, and dig out the embroidery cottons:

You bring the thread out from underneath at the lower left point, then take a short stitch across the apex:

And take a long stitch across the bottom:

I changed to a double strand of embroidery cotton here, as it gave a more satiny effect.  You keep taking stitches across the apex, and this stitch gets slightly wider as you move down from the point:

Pull the thread through, so it lies flat and the tension is even:

Then stitch across the base - this stitch gets narrower with each round:

And pull the thread through evenly...ok, it's a bit tight here:

Keep going around and around until you are finished - cute eh?

Next time I'd probably sew some guidelines for the triangle so it ends up a perfect shape - my triangle is kinda more Eiffel-tower-y!

Have you done any arrowhead tacks before - where exactly do you place them?  And do you have any sewing tips for neat and tidy arrowheads?