The sgian as a weapon for fighting

[Dale Seago]

From what I have read the dirk was held in the same hand as the targe / shield and the other used for the sword.

Yes, as a secondary weapon if you can afford a targe and sword and are using them. When carried as a primary weapon in the absence of a sword, right-handers would probably use it mostly in the right hand, just as they would a sword if THAT was the primary weapon.

I have not ready anywhere about the sgian being used as a weapon and I feel that unless it was razor sharp and used as a cutting or slashing weapon it would do little harm due to the normal length of the blade. The Fairbairn Sykes Commando dagger has a 7" blade which has only one purpose and is specifically designed for that. A sgian is usually about 7" in total lenght including the handle.

Right you are. Opportunities to reach vital targets are greatly reduced with a much shorter blade; ironically this is something I've often illustrated with a 13-inch bladed Scottish dirk when teaching workshops on self-defense with tactical folders having blade lengths about the same as the average sgian dubh. For the latter, tactics need to emphasize cutting (especially large muscle groups, to disable) more than thrusting. Yet this idea may not translate well at all to a historic Highland setting where most of your wee-blade target areas may be covered with multiple layers of wool and linen.