Is there any way that you designers of these foam planes note your changes on your prints? I am not saying write every change down on your print, but at least start putting finish dates on your design sheets. That way, if we ask a question, someone may ask what prints are you using and we could tell them the last prints we used were dated so and so. Another way that we would know if there is a print change could be done by naming the plane with the date finished, such as "Alpha Jet 3-4-13".
Then if you change your print we could look back and see if the date has changed. This is just a suggestion and only a suggestion.
In the design world, some of the companies like GM would save the original drawings and if there were any changes would mark them on their prints each time a change was made. Also, the original prints could be called up and then saved giving it a new letter at the end.
Again, only suggestions to keep us up to date if we were to buy your drawings.