Because your siphons are the same size as your main overflow in this design, you might have problem with such large pipes. The water velocity inside the pipes goes down with increasing pipe diameter. At slow water flows, small air bubbles don't get flushed out & get trapped, eventually breaking the siphon.
I had this problem with my DIY. If I use 2x2" siphons (750gph) the water flow is slow enough that I will lose siphon every few days. <Thankfully no flood, as I have 2 siphons ... the other acts as backup.> Now I use 2x 1" an d no problems.
BTW - instead of using all white PVC
's, you might consider using a clear section at the top of your siphon, that way you cna see if air is accumulating.