I've seen other bellows construction plans that look like a mess compared to yours. It looks like the folds and corners would like to get into place, compared wit Dough Bardell's method. I have already used the latter and experienced that it is almost impossible to get a (conical) bellows that is correct to the millimeter.
Using individual stiffeners seems to be the key to get perfect folds. The trick with the punched holes and cutting out the grooves (see DB's website) will never result in all stiffeners being of equal height (i.e. 1-3-5-7-9... and 2-4-6-8-...) and perfectly symetrical.
I don't know if your method (i.e. let the stiffeners run up into the corners) would work for a conical bellows. I'll give it a try next week. I've got a whole roll of brown wrapping paper to test.