Hello Emathews,
I am sorry but I do not understand the query. Do you want to set the SelectedIndex on load? if so, it is working correctly at my end. Please refer to the attached sample.
If you want to reorder the tabs (make tab2 appear at location 3), then you can do so using LoadLayout/SaveLayout methods.
Please let me know if I have misunderstood your query.
Thanks,
Richa