Hi again,
What I do, when I'm learning a new tune to cover or a new song for a teacher and it's in my higher range, is find the notes in my head voice only and then build from there. If I need more volume to get the 'feeling' across I build that. If I need more mix, I build that. You get the idea. Find the placement first with the proper pitch and then add what it needs for the right effect you are looking for. To build a house you first have to build the foundation. Can't build the whole house all at the same time.
It may sound thin, or whimpy when you first find the placement but that's ok! Bit by bit you make it stronger/better/fuller/raspier/wider...etc.
Something else....let's not forget that when we hear the recorded version of any band, there is alot going on that we don't know about in the production. Try and find live versions of stuff on You Tube so you can get the 'real' sound of the individuals voice. Steve Perry for example always tilts his head to his right when hitting the high notes. Don't know how that helps him but it obviously does.
Cheers and keep on singing! You're a talented guy.