i do not mean to offend in any way, but half of these "fixes" seem ghetto or halfassed.
there is absolutely no reason to have to use cpu heatsink on GPU, cut holes in your case, move dvd drive, add more fans, or reflow the board (using a heatgun)
the 360's worse enemy is heat, so why would you use a heatgun?
there are two flaws in the 360, the X-Clamp, and HEAT (which is an irony because the xclamp flaw produces heat). the combination of both can be quite frustrating. if both of these flaws are affecting your 360, you could be getting redring even after one fix or the other (and you might think you didnt fix it!)
this is what i do on a regular basis, and is a permenent solution, that has never failed, it doesnt look ghetto, funcionality does not change, and (almost) anyone can do it.
-Stock 360 fans are rated for 12V, and they run on 5V. So yes, find a 12V source on the board, its very easy, there are perfect donors on the DVD drive cables, some on the mobo, just use you voltmeter! get your fans 12v power and they will be keeping your 360 cool.
Red+Brown on the fans is +, else is -. do not cut the negative wires, keep them on the plug, and leave them plugged into the motherboard, makes things easier.
Doing this is the easiest, quickest, and MOST effective FREE mod you can do (given you have a tiny bit of wire and shrinktube)
I do this to my box's and the amount of airflow is insane. My box never gets hot anymore, and exhuast air is never even warm. this SOLVES the VPU heat issue.
XCLAMPS, REMOVE ASAP, get m5 .80 pitch screws with 16 1MM thick washers, and 16 1MM thick nylon washers, remove clamps, clean processors and add new thermal compound. I use arctic silver ceramique, i have my reasons.. But when it comes down to it, thermal compound is thermal compound. just make sure you get some to take the heat =)
youtube xclamp fix, many vids online on how to do it.
The combonation of these two eliminates all threats to the xbox (except MUCH more remote errors, which are quite uncommon compared to E74 and 3 rings)
sometimes going into it with patience, pays off.
sometimes adding 13 fans, changing heatsinks and destroying your box, is going way too far
again not trying to bash or talk crap, just trying to explain that some of these things are completely unnessacary.
sorry for the spelling.