Certainly a 6'6 guy gets better leverage and changes things, but I still don't think I would sub him for someone who doesn't know the system even if they are bigger. Personally, I'm dying to see Blackmon log significant reps. I don't know what they need to do to feel confident in his knowledge, but if I'm the dude, I spend the whole weekend, even part of Sunday (Gasp!)with a buddy quizzing me on every call and every position and every play in the playbook until I know it in my sleep. If I'm Holliday, I assign Juergens or someone else to do that with Blackmon until he knows the plays in and out. Gotta get him involved, but if he was the one who lined up incorrectly, IF he is the one...he can't play until he gets it straight.