So I took my old 20L sump out of the system on Sunday July 17th and let just my SEIO handle the circulation in the main tank. The new 29 gallon sump went in last night (20th).
Here is the 29 gallon getting the first baffle of the bubble trap:
I had to silicone this in place first as siliconing this between the other two "down" baffles was not an option with my big hands.
Brian's helpful DIY tip #564: Unfortunately I used old silicone and I had to remove most of it and silicone it again with a chopstick after the down baffles were in place. Always use fresh silicone when doing projects like this, mine was only 3 months old, but still no good. Also, silicone should not be stored in temps above 80 degrees, who knew I actually was supposed to read the storage instructions on a tube of silicone!
Then I worked on the skimmer pump modification. I bought a threaded 90 and drilled some holes in PVC that would be covered by the original sponge that came with the pump:
Here is the skimmer with the new pump mods installed:
This is where I ran into my first and only major problem

My skimmer would fit HOB style, but the input and output pipes were below the lip of the tank. In order to have the skimmer HOB style, I would need to drill the side of the tank.

Deciding that wasn't an option, luckily for me my skimmer can run in sump. So it was placed in the refuge section and it takes up about 1/3 of the section reserved for cheato and frags. But I gain the benefit of if the skimmer ever develops a leak, it will leak into the sump, not onto the carpet, so a fair tradeoff. I'm all about avoiding leaks and wet carpet.
Here is the skimmer installed in sump under the tank:
Here is the right side with the skimmer pump and refuge section and the bubble trap on the left side:
Here is the left side with the much larger return section and bubble trap:
After running the sump for a couple of hours I noticed that some micro bubbles still get into the return, but considerably less than in the old sump. We'll see how it goes after the sump slimes up.
Here is a picture this morning of the collection cup after only 8 hours of running:
VERY COOL 8) There was even about 1 inch of liquid in my overflow bottle. It doesn't show in the picture, but the liquid was a dark green, so it looks like the skimmer is doing a much better job already. Of course the main tank was skimmerless for 4 days, so that may have something to do with it. We'll see how it goes after a couple of weeks.
You'll also notice in the last two sump pics that the wires are all zip tied, man zip ties rock! I think I'll go around my house and zip tie anything loose
B.