[krazy]

The most trouble you're going to get from the radiator placement is that it will be difficult to remove the air from the radiator unless you have an uncommonly fast flow rate through the loop.

A reservoir is not needed solely to contain extra water, as the amount of water leaving the loop over time is theoretically negligible in a sealed system. It is really handy to have, however, for catching air. In a completely sealed loop, air bubbles never get a chance to escape from the water. Even if there is a T fitting, the water doesn't slow down as it goes by, so only the huge bubbles are able to escape from the water.

A reservoir that is large enough for the water to slow down to a near standstill and flow slowly through the res or around a corner to get back out is the best way to get air bubbles out of the system.

An air trap theoretically works fine no matter where in the loop it is placed, as air bubbles travelling around the loop go through every part of the system. Some people like to put them up high, and some people have reported increased pump performance by having a reservoir right on the inlet to the pump. For your setup, I think the air trap would be the most helpful in the upper 5.25" bay, making it a little easier for very large air bubbles coming from the radiator to get to the trap (less gravity-fighting required that way).

My radiator is going to be mounted in the PSU hole on the back of a Chieftec full size tower. It's a single-pass rad, so I will be sending coolant in the bottom and out the top. The upper fitting will lead straight across to a reservoir in the uppermost drive bay, and I'm anticipating very good de-airing performance from the setup. Pics of progress are going to be showing up in a worklog thread one of these days...

By the way; I like the edge trim you're using around the fan hole and the rad cutout. What is it or where did you get it?

Edit: forgot to talk about draining/refilling:

I don't have a ton of experience in this department, as my loop is running in a dishpan while I build components into the case I finally got for it, but I have devised a system I plan to use in my case. The lowest point of the system will have a T fitting with the odd connection pointing downwards. I'm going to pipe this through a small valve and out a port cut through the bottom of the case. In theory, draining the system will be as easy as setting the tower over a sink or bucket and opening this valve. Air will be let in to replace the exiting coolant by opening the filler cap on the reservoir up at the very top of the loop.

Refilling will hopefully be as easy as pouring coolant into the reservoir. It will inevitably not want to flow down into the system, so I'll use the drain valve to bleed the air out from beneath the water. Once enough has flowed down to flood the pump impeller housing, the pump will be able to start and de-air the loop under it's own power. I'll just keep topping off the reservoir until all the air has been able to escape.