I haven't actually seen any pictures of anyone doing this. I would have to completely cut out the lower metal brace to fit either one in.
Anyone done it and care to post some pictures?
I'll post some when I do mine. We'll either make a new panel out of sheet metal with a hole cut in it for the speaker or make one out of 3/4 mdf.

 

yes it's going to require some metal work and some adapters. I don't remember anyone putting 6 x 9's in that area before. I do remember someone putting round 6.75" subs in that area. Definitely make sure you brace anything you cut as that can impact the side impact crashes by altering those metal sub-braces in the rear sides. but you should be able to create something that doesn't compromise the structure.. post up pics! that has the potential to be a sticky! no doubt!

 

I'll definitely post pics of it step by step to show what we did. We're still working out the details. ;-)
I've read about people putting 6x9s back there but no one posted pics. It was kind of annoying.
I'm also making a new floor for the rear that will have fans blowing air over the amps and still look stock and a fiberglass enclosure for a 10in sub that's going on the passenger side area of the trunk right over where the amps are mounted.
I'm trying to go for stealth with this build. ;-)

 

then definitely hide pics of your exterior color or any identifying landmarks so it will STAY stealth sounds like an awesome build! ya got me jealous (good kind) already! liking the idea of a new floor with air ducts cooling the amps but out of the way, i've always wanted to keep use of the trunk but have the amps hidden. yup keep us posted..

 

The 6x9s I have are kappa 692.5i so regardless of if I go with the 6x9s I have or the 8s my friend has its going to sound good and give me the base I'm looking for. :-)