How do you reverse the fans on the unit?

you literally have to physically take the fans out and flip them. Not hard though, I did this after talking to the cloudplate folks. You lay the unit down face down, remove the screws, take the back off, and flip the fans one by one. Make sure the power cables are out of the way, and close it back up. That's it. Super easy as I actually had to do this as well.

Where can I buy a replacement plug?

I would contact the manufacturer directly.

What's the difference between the T7 and X7

The T7 is designed for quiet environments. It won't blow as much air but works great in places where it matters what amount of sound is made. This made the T7 unit ideal for our in house sound rack. We wouldn't want the noise level annoying our patrons. Also a good option for home theatre applications etc... The X7 on the other hand has the ability to move more air and create a cooler rack then the T7 can, but at the cost of a more noisy unit. This works great when the rack is not in a noise sensitive area, for example in a server room. Hope this helps!Bret R.

I have an 8 space rack and most illustrations I've see recommend a unit at both top and bottom. Will 1 of these be adequate?

Mr. Ivey, I can only respond according to my personal opinion and experience with this fan unit. I have mine mounted in a 4 space rack in the bottom location in the back of the rack. My configuration sucks air in from the outside and brings it up through the cabinet to be pushed out near the top. The only real heat producing item I have in the rack is a Mesa Boogie Studio Preamp which has tubes, but they are rather small (12-AX7's and 12-AT7) 4 or 5 of them inside. This setup is not going to produce a great deal of heat anyway, but I wanted to play it safe so I installed the exhaust fan assembly to help the air movement inside the cabinet. If I had any type of tube power amp inside or multiple tubed components other than the one preamp, and was using an eight space rack, I would probably want an additional fan near the top to aid in pulling the warm air out from the inside. If most of the components were solid state, I would probably use only the one fan assembly. I hope this helps in your decision. Thanks and good luck with your purchase!