MY first was an X-kilt with machine, second was hand-made 8 yard with cheap, sleazy fabric. That boosted my confidence no end, but going to good wool required some adjustment to technique.

If you have sufficient stubbornness and good bachelor-level sewing skill, you will be able to do this. You have some fabric that sounds pretty decent, but you are not risking a lot of cash outlay.

The difference in a 4-yard box pleat (vs. 8-yard knife) is that the pleats will typically have more that twice as much taper per pleat in the box-pleat. We're trying to get the same amount of taper in far fewer pleats. The layout on your tartan sett may make this trickier, or may lend itself well to the box-pleat. Pin it up and see.

The knife pleat makes it less tricky to sew each pleat, but there are a whale of a lot more of them! But as we implied, you have the desire to do this, you have showed the ability to develop skills requiring much practice, and you may have a genetic predisposition to (shall we say?) determined perseverence. So, you can do it! Pin up the fabric each way, and make a choice.