I burnt a cpu with the DD Maze 2, and I can tell you it mounts very flat by the screws alone. Just watch the effect the hoses may have on it.
I'd definetely mount the block with the hoses unconnected on there other ends, then carefully move them into place watching if they are moving the block. You can see this very easily if you watch the screws and see if they're moving.
In the end I replaced my hoses with better quality and did a couple test mounts, removing each time and viewing the pattern imprinted in the core and the way the arctic silver squeezed out. If you take a little time and lap the block to 2000 grit like I did, every time you mount it there will be a "picture" of the core (I can read the serial number in the block), and you can tell if it's mounting flat (although each time you'll need to take a minute to buff the ""picture" out with the 2000 again).
All my test showed it was flat, so I trusted it and booted up, this time very cool. Should have checked those original hoses and saved 200.00