Yea been there done that. It takes awile to find something that works well. It depends verry much on how well you grasp the cooling eficiency of the parts you are working with. I started with the same kinds of designs:
first this:
http://community.webshots.com/album/28051709IzZlTDxLyZ
then this with an alpha:
http://community.webshots.com/album/30556976fWLpIMxkEt
finally ended up with this:
http://community.webshots.com/album/35111553UecmAe
Just keep at it this has taken much time and tinkering.