I don't have any personal experience with sumps, but I'm planning on using one with my next setup, and have been reading around a bit.
One thing I've seen is that people hook up the venturi from a powerhead to the top of the siphon, or use some sort of low flow-rate peristaltic pump (I've heard 'aqualifter' mentioned fairly often, but the reviews I've read of it aren't too hot...).
This serves two purposes, to eliminate bubble/gas accumulation in the siphon, and also to help prime the siphon after a power failure.
-power fails, pumps shut off, water drains below hole for siphon break, siphon breaks, excess water drains into sump, everything stops, no flooding, etc.
-power comes back on. the pumps start again, but have little/no water available due to overflows/etc, aqualifter/venturi starts pumping the air out of the broken siphon and priming it, once siphon is primed, waterflow returns to normal and the system can effectively self restart.
I'm not sure if there will be much of a problem with the pump potentially running dry until the siphon is primed again, but it seems this plan is fairly common, so I imagine someone has some experience with it.
this defeats the purpose of the siphon break he is trying to install
but yes u still have to have a priming method,, i actually have two aqualifters.. one on a 29 gallon, one on a 75 gallon. they are fine as long as u use the prefilter AND check weekly for snaills, or debris cloging input/ output holes. if my overflow has bubbles accumulating, its because a baby snail crawled down the airtube and got stuck at the barb for the prefilter. a toothpick fixes this