If you do enable the IC2 or Forestry copper and tin, only enable one set of them to save you some hassle. If you enable both, you will constantly find copper and tin that won't stack until you pulverize/macerate it. Also, once you enable the IC2 or Forestry ore, make sure to disable the thermal expansion ore generation.
Err... will it all work okay if they're all enabled? I don't mind a bit of extra hassle if it'll save me the ore gen problems.