As an update, I was not happy with the look of the modified OEM bracket so I sent an email to Euro Motorspeed concerning the brackets they include in their kit. I ended up talking to Toi and ordered just the brackets. I wish I had done that in the first place! The brackets are of excellent quality and fit the 3.5" Pioneers perfectly. Even though no one ever sees the modified brackets, I knew what they looked like and it bothered me. I know, I have issues

The brackets cost $65 shipped and IMO are worth every penny considering you would not have to spend the time to modify the OEM plastic brackets. The Euro ones are metal and are a perfect fit.