I've always been an offensive guy. When thinking about the other side of the ball, I think I've gone about it similarly to what most do and that's think of what is toughest for us to handle. Obviously, good offenses will have answers, but a defense that isn't stagnant, varies looks and pressures and gets hats to the ball causes us the most problems. I like the base 3-3-5 with the ability to rock down to the 4-2-5. It puts in an offense in a spot where they've got to split the week's preparation time in half getting ready for and Odd and an Even. I also likes that it doesn't require king kong at a defensive end. At least where we are, most schools have more depth and ability in strong safety type kids than they do in linemen. Leaning on the ability to be flexible with those kinds of athletes is a big reason I like this defensive scheme.
As far as the pursuit drill goes. The tried and true team pursuit drill is a good effort and camaraderie drill. The twist I like is having the second group line up as an offensive formation and take their first 3 steps to force the defenders to react to a key before taking off. We put coaches or other players in 6 spots; both flats, each of the deep thirds and the pipe (down the middle under the FS) after the key reaction the ball gets thrown to one of those 6 spots and all 11 defenders have to rally and keep their feet moving until everyone touches the ball.