The problem with narrow pleats in a traditonally made 4 yard box pleated kilt is that the depth of the pleats is only approximately half of the width of the visible pleat reveal. So a 2" wide pleat is only 1" deep, in other words.

Any pleat more narrow than 2" will have a very shallow pleat, and it will be much more difficult to get it to maintain its shape.

Of course you can have a more narrow box pleat and not necessarily sacrifice pleat depth by including more yardage in the kilt. In this case the pleat on one side of the pleat will be rather deep, and the other side will be shallow. This is, in essence, the "military box pleat" of today.

There is nothing wrong with having 8 pleats. Most of my personal kilts have either 8 or 9 pleats. Looks perfectly fine in a box pleated kilt.