Hey just thought I would add this.

I read "pipe siphon by Apollo", the siphon design does seem good, as someone else pointed out you only need one down pipe, I believe the double down pipe is extra "fool proofing", however it seems that the reluctance to use a bell siphon was due to its complexity and diffuculty to get it running properly.

Here is a VERY simple bell siphon. https://www.youtube.com/watch?v=oDzcKgWLRf0

Hope this is helpful