Railroad Crossing Sign - Thomas Track

I am new to 3D printing and modeling, but once my son saw the things I could make for him, he requested a railroad crossing sign.

This sign was modeled in AutoCAD Inventor.. my first model so be kind! :)

One problem I noticed is that for some reason even though the export of the STL is fine, Makerware imports it very small. Scaling seems to work ok in there though, as the hole was still the proper size. If anyone has any Inventor experience and would be able to tell by the .ipt files wha