Just got my JBL's installed. They definitely sound BETTER than stock.
I contemplated the tin snips for trimming the areas required, and started to use them. Did not like the way that the metal was deforming though with the initial cuts. So I wrapped up the speakers in tin foil, exposed the areas that I pre-marked for cutting, and dremeled the areas off.
Worked well. Minimal metal shavings to worry about adhering to the speakers. Am glad that somebody mentioned the shavings possibly being an issue from the dremel usage This is why this board is so helpful.