If you've got the wall space, an L shape indoor enclosure is a great idea.
As far as hot lines work, this is the rule of thumb I follow and it works great for the horses.
Set the hotline to strike below the eyes. Below the eyes, the animal backs up. Above the eyes the animal lunges forward, bypassing the hot line by going forward.
Just something I've learned the hard way with livestock. Hope it makes sense. I'm way tired.
Yes, 2"-3" above top wall hight. I have regular hot line insulators attached to those 1"x3"x16" wooden contractor stakes.
Although thick in my parts, I don't concern myself with birds of prey. The ones I'd be worried about would be the jays and cat birds. They are the peck and tear type birds that do the damage I worry about. Them and wild mice. Again, mice will just camp out and chew causing lots of real injury. As my signature suggests though, those, birds and rodents, stand little chance of getting past the ever watchful eyes of 7 cats.