Like Iowagirl says, it's not just a problem of sweetness, but of consistency, especially with baked goods -- adding an extra cup or so of liquid probably isn't the best idea! However, I've heard of people successfully reducing DaVinci by cooking on low-medium heat until it reaches the desired amount. If your recipe depends on sugar for bulking, you may want to experiment with reduced DaVinci plus a bulking agent like not/Sugar, or reduced DaVinci plus erythritol. You might also want to experiment with erythritol or maltitol (sold as DiabetiSweet), depending on how they agree with your digestive system. Erithrytol is supposed to be the gentlest of the sugar alcohols on your digestive system, but it's only 70% as sweet as sugar for the same volume, so it usually needs to be combined with something else.

Just to stick my opinion in here, though, I think it's not a bad thing that Splenda, and desserts made with it, have some carbs in them. Most of the cheesecake recipes I've seen have 5-8g/slice, which is low enough that we can all fit it in as an occasional treat. However, if we get the carb count down really low, it's easy to fool ourselves into thinking that it's a "free food", and it's OK to eat on a daily basis. I think it's best to have SF desserts no more than once or twice a week, as it's not just a question of carbs but also of habits (and perhaps calories). I struggle with this myself -- I'm on maintenance, so I could easily "afford" a piece of cheesecake every day, but I don't think that daily desserts are really what LCing is all about. I like making desserts, though, and with only two people to eat the results, we wind up eating cheesecake every day for a week. If the cheesecake had the same carb value as, say, a couple scrambled eggs, I know I would have been tempted to make and eat it more often, instead of trying to limit it to once a month or when company comes.