Wayles3,
I have been using RailModeller Express to design a peninsula extension and am quite happy with it. It is free, but limited in the size of the layout you can create. If you like the app you can upgrade to RailModeller Pro, for unlimited size and some additional features. It is available on Apple's App Store. What I found great was the ability to try different size turnouts to see if they would work within the space limits I have. I found I could use larger turnouts than I thought and that made my day. Give it a try and good luck. Glenn