I am toying with the idea of fitting larger speakers into speaker holes beneath the rear seat (sub woofer area). Presently the existing holes accommodate 4" speakers. I was considering replacing them with 6" speakers. The question I have has to do with the mounting. The existing hole has a plastic surround retainer where the OEM speakers screw into. If I remove the retainer, I may have enough room however, if the hole needs to be larger, any thoughts on how I should proceed? I'm concerned about drilling because the gas tank is in the vicinity. I don't know if the lip beneath the seats is made of metal or not.

So far, the good news is that the existing OEM speaker wires have separate grounds rather than one common. Therefore, I can use them with no worries. I will be installing an after market radio as the original one is shot and if working, does not accommodate my audio input requirements.

Any suggestions would be welcome.

Thanks.