I know this is an old thread, but it asks good questions and has good information so it doesn't hurt to answer, right?

I have noticed a more bitter taste with unsweetened chocolate using just Splenda, but it seems if I use better quality chocolate (for me that would be Droste or Valrhona unsweetened baking cocoa, or Ghirardelli unsweetened baking bars) that helps. Also, lately I've been combining splenda and stevia with pretty good results. I have a liquid Stevia called Stevita (I think I'm spelling that right) I just got recently so I'm still experimenting with quantities, etc.

We should be making a trip to Winnipeg sometime this spring, so with luck I can pick up some Canadian sugar twin