Drain setup: General Questions

[Faithinc]

So I've set up a pseudo-Herbie/Beananimal drain system for my 55g. My concern was: When I was setting up my tank, I could not find a glass shop/acrylic shop that could cut a proper over-flow box for the top of my tank. What this has left me with, as you can see from my awesome MS-paint drawing, is a Herbie over-flow system without a box. I've added some grate to the top & bottom pipes to prevent any fish getting into the system... but I am wondering if this system will fail/not accomplish what it should.

So far the system is whisper quite, the loudest noise coming from the hum of the return pump. The single 3/4 full siphon drain sucks about 450-500gph, and my return pumps max 550gph. So far the system is balanced with a good flow (around 500gph circulating)--but its just cycling at the moment with no real bioload outside of the LR/LS.

My primary concern is that I don't have a surface puller dragging water off the top like how an over-flow box would. Because the drain pipe is submerged, and the other is about 3/4" above the water level--the only thing disturbing the top of the water is the power head.

Is this set up ok? or should I drain and see if I can't find an over-flow box. As it stands, I still haven't received call backs from any of the acrylic cutting places I've called for quotes

Addition: I went with Acylic because Crystal Glass quoted me 150-200$ to cut the 7x7" box. The tank is Glas