Excellent! So glad it worked.
As for the 'raft' feature, I just imported the STL file into Solidworks, added it to the model and saved a new STL file. In Solidworks, I create the 'boss' feature but uncheck the "Merge" option. This creates a separate solid body. I then add a chamfer to the inside edges that will attach to the part, creating a joint that is around 100~150um thick. Then I 'combine' the bodies to create a single body before saving the STL file.