well, i know that some standard fan/heatsink combos are 90mm and that is the typical size of a case fan, so i suppose you COULD do it, but no guaranties its gunna have a better air flow than a fan you can buy WITH a heatsink. l8r man.
that'd be what that duct mod he linked is for.......if its anything like my stock HSF that blade is I believe 60mm and spins clockwise....if I were to use that duct type mod he linked with my 80mm tornado (well tornado would probably burn out 60mm motor) so just a regular 80mm fan....they normally spin counterclockwise..but they push the air the same way.....if you get a hold of a clockwise spinning 60mm fan and an 80mm counter-clockwise spinning 80mm fan that push air in the same direction you get MUCHOS more CFM and air pressure.....the result of the two opposite spinning blades cause compressor action....thats why you see still blades on the bottom of the tornados that are turned in opposition