you want a syphon whithin the overflow box itsself, but you dont want a syphon from the tank to the w/d. im not very good at explaining these things, perhaps someone else will chime in.
it will work... but the flow rate will not be that great.... and you might need a smaller return pump... might as well go to home depot or lowes... make a 1~2" "U" pvc pipe... to siphon (overflow) the water out..
an overflow works by siphoning water to a box hanging off of the back of the tank. The overflow then flows into a drain which eliminates the chance of draining more water to a sump than the pump is able to return. If you just started a siphon like the above link, then you couldn't match the flow with your pump and either the tank or sump would eventually overflow.
if you make a syphon it will never stop untill the syphon is broken.. which means it will drain your tank untill it starts sucking air...
thats why people use overflows.. its not just a neat name.. it also means it only drains water that "overflows" (think of it as the small hole in the bathroom sink.. not the main one.. but the small one thats up near the top)
overflows also auto restart.. which means if while yer at work and the power cuts out for 10 seconds while the power company is working on something.. you will not come home to a wet floor.. with a syphon someone or something has to start it everytime it stops...
if you are going to spend that much money just get a premade HOB overflow.. it will cost you $10 more and work a million times better
or for half the price you can build one out of pvc (look in the DIY section theres a huge thread all about it)