In case it helps anyone, I managed to do this with 5-10mm of clearance left. I did the same thing, sandwiching the speakers between the fastener points and the adapter from Hein. It does sound better than stock, but it wasn’t a dramatic difference. I might need to add a sub.Super informative, thanks for this post! How are you liking the c2's a year in? I'm thinking of just swapping out the factory front door speakers with the c2-650x coax versions and calling it a day.