Just a simple modification that may help with first layer issues or when work cooling not required. Place closed gate/valve in and when/if required pause printer and replace with open gate/valve. Or as I have found in use if gate does not foul anything move it in or out to control air flow. P.S if you rotate duct in thingview you will see how it works ;) Added V5 Same tolerance as used in original model so should be ok Pic shows V5 version. Heatsink diameter is 24,64mm and fits nicely. Probably should be longer so may edit chineseclone version from original Thing :- http://www.thingiverse.com/thing:839620