i just used cardboard and indead the dvd drive was alot cooler then without the shroud modification.you need to divide the two fan's in the back, there is so much sucked trough the cpuheatsink.
Had two rrod 360's that i couldn't fix, they kept coming back.With the shroud modifications and the gpu fan on 12v they work great, now problems.the air that flows out of the back is much hotter.so there is more cooling going on.
My only problem with this mod is when you turn it off, with a shroud on the heatsink it is unable to dissipate it's heat.so after a long session of gamen you'll have to set it in his dashboard for a minute or 2 (still 38 degrees).there is a mod on rbjtech site to modify(9v battery
) your fan's to let them run a little bit longer after you turn off your xbox 360.maybe somebody can figure out a way with a usb device.you'll notice when you leave your usb controller loader in the 360 won't shut off completely.it keep on charging your controller and still let the fan's run.When you pull out the usb loader it will shut down.somebody an idea??usb stick with a 555ne chip.