I thought I heard my name mentioned! After reading this thread, and looking at the style 4 saber, I'd have to say the best way to build a hollow version would be to use Novastar's suggestion of two of the 1.5 sink tube adaptors, and blade holder #1. Also use a piece of 1.5" sinktube and 1.25 sink tube. All of the electronics will fit inside the 1.25 tube. You'd assemble it in a similar way as in my picture, using the split ribbed tubing instead of the slip-joint poly washers. Following the instructions at BYB, you would replace the 3/4" dowel with the 1.25" chrome pipe. Getting the ribbed tubing to fit might be a challenge, but it looks do-able.

Here are the parts I used from the store when I put that saber together:
style 1 blade holder

1.5" sink tube adaptor
If you're doing a double bladed saber, you'll need two blade holders, and 4 adaptors. Not exactly the $20 price range that BYB quoted, huh?