What are your thoughts on the recovery location, the familiarity of the perp with the grounds and the way the girls were positioned?
He is familiar with the location, whether it be a party place or a place his father took him hunting/fishing in his youth. He hadn't gone back there frequently, but now after the murders, he has likely returned a time or two. Most likely within the last year or two, as not to call attention to himself.
As far as the positioning of the girls, since we don't know the exact position of the bodies each, we can only assume one of many theories:
-He placed one girl, couldn't see where he put her and just happened to place the other further away
-Depending on the state of decomposition and when they were placed, the body could have been moved by an animal
-As he finished placing one, he heard a vehicle/person, was spooked and 'tossed' one from where he stood
-The girls were both alive when they arrived at Seven Bridges, he killed one, the other ran and he caught up to her where she was found
Not knowing X amount of other details, I couldn't tell you for sure which theory could be close to correct or if any of them are. I do however commend LE for keeping so close to the breast on the details of the recovery. It will help ensure that if someone slips up, they have a significant amount of information that can nail their coffin shut.
Do you think the offender immersed himself in the search or investigation at all?
Yes. Most likely he was there at the vigils, perhaps even gave Heather, Drew, Misty or Dan a hug or kind words, visits the Angel's Park and closely follows the case. BUT! he is sure not to let on to anyone else just how closely he follows it. He doesn't "care" or feel anything toward what he did, but he is paranoid of being caught, so he may put on the facade of sadness, but is really basking in his 'accomplishment'. He delights in the fact that he can attend these vigils, memorial rides and such, and no one knows the truth. It's a thrill, a push of endorphins, a high, for him. That he knows something no one else does.