Sump Design Question
 

I need some ideas on designing a sump out of a 55 gallon tank measuring
48" X 21" X 13". The first compartment would hold live rock, the second would house the skimmer and thermostat, the third would have a baffel from the top for a bubble trap and the forth would be the return. I just need an idea of how long each section should be if anyone's ever built one out of a tank this size.