re: Do you believe Perkins at mike is set in stone or will he be moved around situationally?

From Football Advantage site...sound like Perkins position to me.

"The Will has a freelance-type role in the defense.

The job of the other two linebackers -- the Mike and the Sam -- is to clog up blockers and shield the Will from offensive players. If they do this properly, the Will will have more freedom to roam from one sideline to the next. This is necessary, as most defensive systems will ask their Will to be the playmaking linebacker. A great Will can break up passes, deliver big hits, and disrupt the offense. Considered the ball-hawk among the linebackers, the Will is typically the best pass rusher among this group. They may even be the best pass rusher on the team. In man-to-man coverage, he'll typically match up against second or third receivers or running backs. In zone coverage, he'll drop back into the mid-range zone. Against the run, the Will's job is to identify the ball carrier early and attack him on the most direct path possible, without letting the ball carrier get behind or outside. The Will should be free to roam around the field and not be locked into certain responsibilities or zones.

The main trait that a Will needs to be successful is athleticism. He needs to be powerful, of course, but most Will linebacker's will be faster than they are strong. With that, it's not straight speed that they need the most; it's the ability to be quick and disruptive by avoiding blocks more so than taking them on. He'll line up on the weak side of the field and have the freedom to roam around the field and make big plays. Those who become Will linebackers need to be fast, quick, and very athletic."