Thank you LSUFAN. I grabbed all the parts and tools and headed to the office today. Cut thin rings to slide into the syphon toothed 90. Got there and realized the 90's are 1 1/4" not 1 1/2" so of course they didn't fit.
Hummed and hawed and decided to make changes.
I'm swapping the syphon and open channel. This will allow me to 1) completely put in a new syphon 90 with no slots 2) allow my syphon to have a near vertical drop in the back of the sump via 2 45's rather than the current set up where it travels forwards to the front of the sump (even though it fully syphoned with the current setup when I blocked the open channel).
I had all the parts except I need to pick up a valve and a bulkhead. I just have to replace the T with a coupling and replace the plumbing forwards into the overflow box. Threaded bulkhead this time!
The top terminal caps are just threaded with teflon tape so I can easily switch them so the air tube remains with the newly allocated open channel.
I will take your advice and hopefully be able to tune it once I glue what needs to glue and allow it to cure. I will update. Thanks again.