Ted, sorry I didn't get back to explain sooner, the double knife pleat is simply two knife pleats laid on top of each other, then the normal pleat spacing, then a further 2 knife pleats on top of each other, and so on.Above the fell line it just looks like a normal kilt.So in my kilt ther are about 36 sewn knife pleats, but they are grouped in pairs making 18 actual "pleats". This means that there is a lot a fabric to move and swish below the fell line,much as I imagine the fabric in a double box kilt works as well.

Re. the ironing, not much of a problem, all the edges of the pleats are sewn so they hold together very well, if I holdthe bottom edge firmly the pleats do seem to lie flat and then it's easy to press them.

I've made many kilts, this one was a bit of an experiment to see if I could get more swish from a non wool fabric, and it worked very well, the only thing is it's a lot of extra work.