I have a piece of tartan cloth - Modern Morrison, which is 54 in by 4 yards, and having fussed about with it, the only thing I can see that might be a problem would be that you could be resticted in how you arrange the upper part - it depends on your proportions.

Depending on how you want to fold it, and to some extent the size of the pattern if you want to fold it to a line in the repeat, you might possibly need bore than 4 yards, but if you intend to pleat it up fairly randomly and not very large pleats then 4 yards should do.

I have some tartan like cloth that is 60 inches wide, and if you can find something suitable you might like to consider getting a piece to try out. The 60 inch wide material tends to be wool blends, and not have a kilting selvage, but it might be a good idea if you can pick up some 60 inch wide fabric cheaply to try it out first. You are more likely to find a cheap 60 inch fabric than a 54 inch one, at least you would be here in the UK.

Another alternative is to use an old sheet and cut it to size - it will not be the 4 yards but it will give you an idea of how much of you the 54 inches will cover.