1) Simplify. Put all features and functions into three buckets "must have", "nice to have", "not critical". You make sure all your must have items are fully included in the development. If you have a slip in effort then the first to go is the not critical and then the nice to haves. In effect your contingencies on reducing the scope of project work to be your hedge with time and money. DON'T TELL YOUR ENGINEERS THIS. You want to keep the pressure on the team for full delivery.
Don't be a creep. I'm talking about scope creep. Often entrepreneurs get really excited and creative in the R&D or development process. This invites lots of "what if's and wows". Don't do it unless you just completely and utterly missed your prioritization. You need to realize you're jeopardizing your project with changes.