Cyg,
I would not do it. I own a variation of this, a rebrand from Chieftec and others (Model BP-SATA2131). I've had them over a year now, and the fans are not only noisy, near useless, but are giving out as well! The ventilation is just horrible. I've read one guy reversed the direction of his fans to some positive effect but the gains are just not worth messing with it. I was also thinking of replacing the fans with better/quieter ones, but these are not standard 80mm fans.. they are 15 or 20mm thick... whereas the standard 80mm case fans are 25mm. There are some on the market that are this thin but they are expensive (20 bucks per) and do not have the half the power of the originals. So again I repeat, don't do it or worse case: return it.
Optimally, I'd like to replace these with just an open slotted mobile rack and use case power/SATA directly to each drive. I can use a bunch of quiet/cheap fans hung on a cross bar for much better ventilation. Problem is- I cant find any open mobile racks on the market. If anyone knows an open/slide/slot rack that suites 3 in to 2 (or 6 in to 4) please post it.