I took small drywall mud containers, mounted the speakers in the bottom, cut the tops off, leaving 4 'tabs' in the plastic.
Cut 4 slits in the kickpanel, put the tabs through, drilled holes, riveted them.
Covered with cheap thin black carpet/fabric I had laying around.
Only issue is vents do not open all the way. Even if I just hold the speakers up to that area without the kickpanel on they stick out the same distance.
6.5 speakers, at least these, are pretty darn big, but the sound is fantastic.
I might swap in the molded kickpanels, but I have 3x5 speakers in my truck, and was unable to find a set that has great sound.