I saw some of that material up on ebay a week or so ago. Nearly picked it up myself!

whether or not it is cavan, it's gorgeous

As for 4 vs. 8 yards, 4 yards will have fewer, wider pleats, with less material between the pleats.

However, after finishing my 4 yd macfarlane box pleat, I really like the feel of the four yards, and any I make for myself will probably be 4-yarders from now on, and a 4 yard box pleat looks a little better than a 4 yard knife pleat, to my eye.