I don't know if we can do something as simple as renumbering the modeldatas, because the stages don't have the correct quantity. Fixing them to work in Siege might take substantial rebuilding of the stages inner parts, and I'm not sure it's worth trying to learn all these things just for this Wii Sports set, nor does it sound like a good beginners project.
It's actually really easy to get enough modeldatas. Just follow that link in my last post, kay? Follow the instructions in that post for each modeldata, read my last post to know how to change the modeldata number.
BTW, you won't be able to put FD over STGEMBLEM_00 because FD has 2 modeldatas, and STGEMBLEM_00 has one.