Kenwood DVD/Nav install, 2002 4runner

I'm installing a KVT-815DVD in-dash LCD and KNA-DV4100 Navigation unit in a 2002 4runner. I've done my share of head units and alarms before, so I'm not worried about the wiring, although there is an awful lot of it. Right now I guess I'm looking at putting both hideaway boxes under the driver's seat; there's a hideway box with all the connections for the in-dash unit, and the nav computer box. All the connections to power and the speakers go to the hideaway box, which is sort of annoying but I guess makes sense. Any other suggestions on where to put these things in a 4runner? I saw one post which suggested putting the nav computer in the lower DIN space in the dash, although it's not a full DIN width and doesn't have mounting holes for that. The nav computer needs to be level and stable since it has the gyro in it. If I do mount one or both of these boxes under the driver's seat, how do you typically secure them? There's a raised rail towards the front which is hollow, and I have no problems drilling/screwing into that, but I'm a little hesitant to start randomly drilling into the floor. I'd lose some space doing it, but I think I've seen something about putting 1/2" or 3/4" MDF under the carpet, and then screwing into that? Thanks for anyones input!

Look under the car for brake/fuel lines, and use self tapping screws. If you are worried about moisture geeting in, seal from the underside with silicone. GPS/NAV control boxes must remain stable, and be mounted no less than 5? degrees off of axis. Make sure your sh!t is straight and secure, or your navi will be screwed up.EK Civic

security

no audio

you won't need to access the navi box unless you regularly travel over the east/west line on the DVD rom discs. so you can bury them wherever there's room. under the seat is fine, although I wouldnt use MDF since it soaks up moisture like a sponge. you don't want a moldy piece of MDF stinking up your carpet. try using the supplied brackets and maybe some plastic or aluminum spacers to securely mount the boxes under the seat.car audio pays my bills...