Oh my, this place is kinda dead isn't it?
To answer your question, I'm not sure if corn starch is Core. If it is, then I say go for it. There is significant disagreement amongst the Hard Core on such topics. Many will say that if the end result would not normally be on the list of approved foods, then it's not core. This prevents making such things as cakes, cookies, and other high-calorie goodies that one might over-indulge in.
My thought is, if you can eat such items and still lose then why not enjoy yourself.