I think knife pleats personally. Since it is a darker shade of black watch, there won't really be a strong-contrasting dominant stripe in pleating to the stripe such as you see in Tobus' picture of a MacKenzie/Seaforth.

I agree that military pleats are superb. My next planned kilt will be in FitzGerald Military Tartan and will definitely have them (although I also love the look of Lady Chrystal's double box-pleat), however the beauty of line-pleating is in the "reveal" when walking.

With so much material you could have an excellent knife pleated kilt made with dense pleats which will deliver a splendid rear view and a wonderful motion (dependent on weight). What a wonderful quandry to be in however! Be sure and show us pics once it is made!