Hey, cracker! Nice to see you here.
I was able to fit 6.5" speakers in the stock mounting location. I used vacuum tubing as standoffs so that the cone wouldn't hit the smaller hole, and then I used the mounting holes that were on the speaker for a 3-point mount. When speakers can be mounted onto a car using 3 points, they get the bottom two, top hole, and then the first two holes along the top and the top hole also at the bottom. This gives you a 4-point mounting setup that lines up perfectly with a 5.25" speaker's mount.