Assuming 135Kt ground speed and 4.5hrs endurance:
KOSH - 3M7 (Lafayette, TN) 460NM - 3.5hrs (Spend the night if too tired. If not then continue on)
3M7 - 28J (Palatka, FL) 466NM - 3.5hrs (Spend the night. Nice airport, inexpensive fuel, good hotels and good food. We can even meet for dinner if the timing is right.)
28J - KMTH (Marathon Key) 297NM - 2.25hr
KOSH - 3M7 - 28J - KMTH
My 2 cents.