[384drtysteve101]

Im am assuming you are entering in the 3d design contest
The rule for this award cleary states "If you enter in the 3D design category your entry MUST include use of at least Autodesk Inventor Professional 2011"

So technically you can do what you explained becasue you are making it on Solidworks then converting it over to Inventor. You would just have to construct part of it in Inventor, but none the less you still used Inventor 2011. But this wouldn't be in FIRST spirit, cause your entering Autodesk contest using Solidworks, which doesnt sound right at all.