Here the way I did it. The parts are available at Home Depot or Lowes.
List of Stuff:
1. Roll Of Aluminum tape
2. Somekind of gromets or footstool rubber bottom leg thingies. Anything that can be glued to the bottom of your fans that will hold the fans aout 1 inch off the radiator.
3. twist or zip ties.
Instructions:
(1)Glue the gromets to the bottom of th fan that does not turn. This will be your structural integrety. (2)Use swist ties to hold the 2 fans together. The 2 fans will now function as one. Add 2 more 80mm fans, a total of four, and you will have the equivalent of a 160mm fan
(3) Place the fan unit onto the radiator. (4) Place the tape around the radiator and fan to form the shroud.
Aluminum tape is really think aluminum foil with an adhesive suface on one side. It is true duck tape.