Are the brackets needed when installing an aftermarket single DIN head unit on evo 9? I installed mine without them since the screws were stuck and I couldn't remove them from the oem head unit. The mounting sleeve seems sturdy enough to hold it up. This is for non-MR stock location.

 

Yes you want to use the factory brackets, the plastic front plate isn't strong enough to support the deck, or at least I wouldn't try and use the cage. You could maybe get away with it if you are using a mechless head unit, but I don't think i would chance it. The cage is tempting to use though because it makes for a nicer flush install. Over time though the vibrations and weight of the unit will certain cause issues with the radio and it will sag in the back. Just a little FYI the factory radio harness does not have a ground. Even if your metra or whom ever wiring harness adapter has a ground in it, you will still need to run your own ground to the chassis for the deck.