VERY NEW NEWBIE HERE, i have a au fairlane now and i want to put replace stock 5 x 7 with 6 x 7 in the rear of it, just wondering what you guys would do it? there is a gas tank so i think grinding a larger hole is not possible.

It's illegal to modify your parcel shelf metal so if you ever get defected and they check, your car won t pass. Also 6x9's crank so loud that they take away from your front stage and make your system sound crap. I'm actually putting 6x9's in the front doors of my get around lancer right now. I'm running 6.5" component and 6x9 in the door as a midbass woofer.

I'd run a 6.5" with an mdf adapter at the rear or keep the 5x7 standard and spend the money on your front stage if you can.

I have 6x9s already and was trying to save some money, do you mean modify as in the structural integrity of the shelf? cause i have 5x7 to 6x9 adapters, they are crappy and made of plastic. and was going to reinforce it with 6cm Wooden spacers because the adapters Cone like shape let it fit right in. Also I was gonna make a few choice holes in the front for 6.5", would the 6x9 still make the system sound bad?

It does take away from the front stage as mentioned by justlikemusic, but if you want to reuse your 6x9s and the adapter, might as well. Set the fader on the head unit to be front bias, not a complete fix, but would make your front stage better.

With the adapter, is it possible to put it under the parcel shelf carpet? If you could, it will make it neater and give it a stock look.

Gas tank in the back takes up a-lot of space so the speakers cant be too low, im going to try and get as much of the carpet in its place as i can, i will play with the fader when i get the speakers in, Cheers