Hey man, super efficient, clean build and good spread, nice work!
@Positivity curious what did you mean regarding hole saw? (Edit I think I get what you mean, a one piece shroud with opening for fan?
@tightpockt I think you are right regarding shrouds, probably the most efficient way to implement them would be flat to the surface of the fins and sealed off on both sides of the fan. I may have confused the issue by encouraging only a partial shroud in the case of a fan failure. For long heatsinks, this is what I had in mind for a partial:
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However, even with fans at 7.5V it works very well without a shroud. Ops is at 12V so I expect plenty of air as is. Probably the main benefit would be that you could run the fans at a much lower fan speed.