i'm planing to change the 2 X 25mm fans to 1X 40mm lower speed fan installed at the middle of 2 heatsinks. i will test this fashion on the 2nd batch.
about the heatsink, there is another issue. i must test the boards for hundreds hours before ship them, so i must install a heatsink on it. if a use thermal grease, it will get the boards dirty and negative affect when install a heatsink with 3M thermal tape, because the grease is hard to remove completely.
any suggestion?
One larger fan is likely good idea. No issue w/ YOU installing thermal tape but if you have standard mounting holes then the heat sink & thermal tape could be replaced different heatsink and/or thermal grease.