i mostly use the Wilhelm method which has you use 2 (1mm) washers on the top of the mobo, i don't use any under and that's just my preference. Also I line the edges of the mobo with a credit card/ phone cardof a thickness of .7mm to ensure even distribution of pressure. I was getting the same problem when I did my first fix and it was because I didn't use the card pcs and because I didn't bake.
Here's the link to the tutorial, this is ver.2 and is more in depth, if you want just use it to understand the "credit-card" placement idea, but i recommend following it to the T, and if you really want the fix to stick reflow the chips first, second link.
X-Clamp replacement:
http://xbox-experts.com/e/tutorial.php?n=xclampengReflow Tutorial:
http://forums.xbox-scene.com/index.php?showtopic=651407Hope this helps and best of luck to you. Follow the directions exactly and you should be golden for a lot longer than the average x-clamp fix. I have repaired quite a few with these methods and have had not problems yet.
Also you can add the pennies, but I don't recommend adding more than 2, this can cause flexing which you don't want.