The problem of using sucralose is that it is an alcohol of sugar and will not react the same way as sugar does with other ingredients. I used sucralose as a replacement for sugar in a pecan pie. There are plenty of other sugars involve. Using sucralose without adding baking soda caused the pie to foam terribly. Adding a 1/2 teaspoon of baking soda to the recipe eliminated the foaming but also caused the pie to come out much darker.I know that the sugar is important for things like browning and moisture, but are there other reactions and stuff that I don't know about?
Oh, and I of course never use the substitute for making candy. Ever.
Using the 1/2 sugar, 1/2 substitute ratio has always worked for me.