UPDATE In order to use this as an "inside connector" simply set the Inside radius to "0". Set the Outside radius to whatever fits in your tube. No function change. Just further instructions in reply to something.
This is a version of a multi-connector creator designed for use with Makerbot Customizer. Customizer will generate a connector for any number or rods at any angle (nearly) of any size with any thickness. This thing will continue to be added to and improved until the dead-line. I would like to give you individual arm parameters.
UPDATE You now have individual placement of any angle for up to 30 arms!!!
UPDATE I have now added a sample STL made with customizer to the downloads.
UPDATE*** 2.1 now generates connectors for Triangle, Square, Pentagon, Hexagon, Octogon, Circle. The back edge of the join is a bit rough on most except the circle but I am constantly improving this thing.

UPDATE*** I have added a heel to clean-up the back of the join.