... AND, that 4th added year of FM residency will be unfunded. CMS funds family medicine residents 3 years to complete their training. If you switch programs, the new program must be willing to eat your salary that 4th year, which potentially makes you untouchable.
Now, had you switched from surgery, for example, after 2 years of residency, you would be ok since your funding through CMS is 5 years. 2 years will have been spent on surgery, then 3 years spent in family medicine.