You need the side mounts to do what you are suggesting
The drop in mount is for the very top, which you could use with an extended top cover, to get a total of 3 rads up top. But let me tell you, that would be extremely top heavy.
If you used the top mount for fans only, you would need the 30mm top cover. If that is something you may want, it is cheaper to get now than to order separately later.
Hope that helps, GL