If your tweeters need a custom fit then a tweeter ring is your best option.

Pipeman's Installation Solution Tweeter rings/adapters are CNC milled from top grade MDF for a consistent quality assurance. No more spending time making your own speaker rings and cutting yourself. They can easily be customized for specific sizes and applications by being filed, sanded, shaved to size for a perfect fit.

Please make sure to double check the cutout diameter needed for the specific speakers you will be using.

Features:

2 Pair of Tweeter Rings (4 Rings in total)
Hole Cutout: 2 3/4"
Outside Diameter: 4 1/4"
Made with 3/4" MDF
Can be used for fiberglass projects