I Re-enact with "Montgomerie's Highlanders", the 77th Highland Regiment of the french and indian war. We wear the Feilidh-beag in the Black Watch Tartan. The "little kilt" is nothing more than a Feilidh-mor with the extra material cut off. So it's exactly the same, i.e. the aprons, the pleats, etc. except it isn't as "modern" (buckles, straps) as a modern formal kilt.

When the highlanders came to the colonies to fight the french and indians on behalf of the crown in 1756, they first wore the great kilt. They quickly learned that fighting in the mountains of western Pa, N.Y. and Canada didn't lend itself to the bulk of a great kilt, so they cut the extra material above the belt off. Hence the fillabeg.

Not much difference.