I exported it from MOI to STL. I had the world scale set to mm and scaled the ship to 31 mm before export.

I then used a recommended service, www.printapart.com. I uploaded the stl file (it was zipped) and the service properly read the file. It asked what dimensions my 31 was. I selected mm from a drop down box and then they gave me the pricing and shipping information. The part was ~$45 US, and was shipped the next day. I was very satisfied with the quality of the finished piece and www.printapart.com in general.

I am looking forward to creating the rest of the fleet.

Phil