hivel37,
The Taco Hold is useful when you have to shoot without a rest. It does use a rifle scope and you can successfully hold a 20 power scope steady using the taco hold. Of course, it does take practice. I have used it with hot loaded 357 mag bullets from a 10 inch barrel and it worked ok but the scope did lightly hit my shooting glasses. I mostly use it with a 22 Hornet and have used this setup when hunting ground squirrels.
To do it, You grasp the bell of the scope, or the barrel, or both barrel and scope, with the weak hand. The strong hand holds the grip just like normal. In silhouette competition, you cannot hold your arms close to the body for support, but in a hunting situation, I would hold them in, next to my body for added support.
Sixgun