i first thought of this as a last resort option for HD2.
The normal procedure would be to de-solder the qualcomm chip and reball it, then re-solder it back. This is kind of impossible because there is no BGA former for this chip in order to place the solder balls on it. Furthermore... there is that resin that prevents removing the chip as it melts at a higher temperature then that of the solder joints. If the chip would be heated at that level it would most probably die out from overheating.
So, with a motherboard replacement as the single most viable option, i had nothing to loose when i first attempted this "mood" (i could not use a phone that cannot work at 25-30 degrees ambient temp).
This procedure includes some experiments, proper placement of materials, it's a bit trial and error. Once it was done, it saved my phone, but as being the single example of this working, i can only state that results can vary.
Try to apply some sort of pressure between the cpu, it's metallic shield, the custom made cooling system and the back of the display. All those components must be in perfect contact from a heat transfer point of view. Pressure is almost as important as the cooling system itself, but too much of it can be dangerous for the display - you have something hard pressing on the back of it, thus making it more sensible to outside pressure (more likely to break in case of impact or some mechanical shocks). In my case, if i make a heavy push on the buttons, there are some color spots that appear on the display suggesting pressure is being made on that area. The spots aren't permanent and i never push hd2's buttons that hard - to make those things visible, so it's not a problem on it's self. But it's an indicator on how tight things are inside there
Good luck and i'm hopping for good results.