Certainly the obvious is to develop in 2007 if you have 2007 users. However, should I expect not to see a split form positioned on the bottom (or top) when developed in 2013 and opened in 2007? I can position it on the side. I have tried dropping and re-adding when on 2007. This seems to be a basic functionality that should be the same over the versions, but that a weak assumption on my part.