what do ya think ?

hi all !
first time sump tanker !!
just wondering if you guys and girls can give me a idear on my very basic plan for a sump tank ?

first the spec .
main tank 84x39x36 (l,w,h)
and the sump tank will be 72x24x24
the main reason for going over to a sump tank is to increase overall water volume and filltering capacity (out with 2 fx5s)
.
i would like to keep it real simple. so my plan was to get the main tank drilled in the top back corner and have a simple gravity feed down to the sump via a 2 inch dia boar pipe with a anti syphone hole just under the water level in the tank and a adjustable valve on the sump end of the pipe (to adjust to the pump speed )
and last of all a float swich on the main tank to shut of the pump should the water level in the main tank get to high .
will this work ok ? and have i missed anything that may leed to flooding ?

as said very new to the hole sump tank thing so any input welcome ...........ps no lol,in
thanks all

ahh smart i see what ya mean mate !!!
thanks
so my plan hold's water so to speak lol
ill do away with the down pipe and anti syphone hole in the tank and just fix the pipe strait to the hole in the tank .
any idear how the flow charts work for the sump feed work ? with a valve at the end i can slow the flow down but would be nice to work out what the max flow rate could be with the valve fully open on a 2 inch pipe .
thanks againg fella .