Since you own the other post I responded too, I would keep the probs near or on the drives. SCSI drives *must* have plenty of active cooling. If they get too hot they will pop!. Your chip-set should have it's own temp sensor to read off of.
I thought the question was clear enough so now I will phrase it another way.
The question was where on the drives would be the best place the top or the bottom. And if on the bottom, then on the bottom of the hd drive casing or on a chip of the hard drives electronics.
I have the cooling of the drives covered. They are in a P180 case and they have a Silverstone 120 capable of up to 100CFM pulling air through them. I traded out the Antec Tricool 120 for the Silverstone.
These are going to be SCSI HDD's. I should have mentioned that, running of of an Adaptec 2200S/64. They will be located in 2 different areas of the case 4 will be running at 15,000RPM and 2 at 10,000RPM. I am sure they will be fine because they will have 120mm fan blowing on both sets. I just want to have a good idea where to set the fans for adequate cooling then put the thermistors elsewhere for permanent readings. The VRM spot is a great idea.