As far as overflow designs the bean animal design is superior to other designs for many reasons. Not only are they virtually silent but they are safer, beings that they have an emergency drain. If your still in the planning stages I would try to work on the bean animal setup even if you have to drill a couple more holes. I'm not sure I understand what your other idea for an overflow was but I'm assuming you meant using a coast to coast overflow. This will be very satisfying when you get it all finished and I'm glad to see you are taking your time planning this build. Here is a good thread from a member that used the bean animal design on his tank.