The only problem I encountered was that the housing was slightly larger than the factory hole. Rather than bust out the dremel and make a huge mess, I used a reaming tool to enlarge the hole.
I placed a drain pan under the hole to catch all the swarf and after about 5 mins of reaming the hole was 2mm larger and the sub dropped in.
I also lay down some dynamat for good measure - a 36mm impact socket wrapped in a microfibre cloth made presssing the dynamat down very easy. No pre-cutting, the sub, centre seatbelt and child restraint bracket holes were cut in place.
I have a spare Dynamat 10425 Xtreme Wedge Pack (457mm x 812mm) if anyone wants it - $30 pickup in Sydney. Otherwise i'll just return it.