I have the same instructions Lenny has that tell you not to glue in the tubes. After his experience of making one and having it out of round I decided to try it and glue in the tubes. The only reason I can see for not gluing in the tubes is the tube would come loose during assembly. I found that if you glue in the tubes, then during assembly support the smaller tube ( I used a transfer punch ) there was no problem.
I turned mine between centers without bushings. If you cut the blanks to as close to finish size you can square it up with a skew. If necessary finish trimming the tube with a file, just don't touch the wood.
Here's mine.
