11 bottle connections
 

I know this has probably been talked to death, but I think I have a pretty good solution for those folks who cannot get the thin wall to stick their bottle caps into.
The answer I came up with is to not even worry about the thinwall that the bottle caps sit in. In fact I don't even use the bottle caps at all. I found that I could use a 1/2 inch pvc flush mount adapter glued into the elbow and then just glue a short piece of 1/2 inch schedule 40 pipe into that. The bottle fits very nice and snug down on this pipe. Everything is schedule 40 and easy to find at the Home Depot. Some aquarium silcone seals it up and that's that!
While snug and watertight it's not so tight that you couldn't break it apart if you needed to replace a cracked bottle.

great idea, thanks for sharing!