went to install my pioneer double din tonight and had some issues using the original brackets. it seems as if i need to cut down some tabs and possibly make new holes. is that the norm? also, whats the consensus for filling in the gap below the radio? would it be easier to just modify a single din kit?

 

I just installed a double din pioneer unit and ran into the same problem although I have an FD it's pretty much the same. You need to buy Pioneer's ADTVA133 2 Din Installation Kit. This kit took all the guesswork out of the install.

 

I am thinking of a double Din Pioneer unit too.
which one did you get?(I have an FC also).

I had 2 pioneer single DIN in the s5 mounting spot.
I used just the sides of the old stock radio cage to hold it in.
I found some areas on the deck and EQ to put short self tapping screws and drilled the stock cage.Then I used the screws to secure it all together.
It may not be what you are after but it's a suggestion.