No not drilled. I have hob
with similar mechanics to cpr overflow.
The mechanics are simple (to me).
Part 1: If the siphon tube/section has a a nipple for a airline hose then you just need to seal it. Easiest is put some airline hose on it with a check valve($1 @ walmart) on the other end of the airline hose. This will prevent air from interning the siphon through the nipple and thus preventing siphon loss in the event of power failure.
Part 2: you need to match return flow (after headloss) to the rated flow of your overflow. If you have enough flow going through the siphon any air bubbles that enter the siphon will get flushed out. If not enough flow then the air bubbles will accumulate enough to form an air pocket and break siphon.
Part 3: If your return pump is undersized or you don't have the right sized plumbing( more on this next) for your return lines then you will not have enough flow and you will need the aqua lifter to suck the air out.
Part 4: Plumbing has to be big enough to maximize the flow from your return pump. Mag 7 for instance has a .5" threaded output but you need to at least double that to 1" plumbing for maximum flow As per mag drive manufacturer instructions. You will need to look into plumbing sizes for your particular pump brand.