Have seen these made of wood, looked fun so I designed and printed some myself. there were a few design changes (think like 10 ;) ) and found this setup to work the best in shape and weight and such.
• new version that will use M8 nuts instead of bolts for weight - http://www.thingiverse.com/thing:2214933•
- print end caps solid, 100%infill using a flex filament ** - (can use regular filaments but will need to put a soft pad something on the end after)
- **print center in what ever plastic you want, but needs to be around 4 shells, with 4-6 top bottom layers with ZERO infill...
End caps are pre-threaded to take an M5 bolt for added weight.
note- just added a "CapWithBridging" file, what this is is a thin, single layer membrane added where the M5's head stops and the threaded area starts so the printer should bridge the gap instead of making the bit of spaghetti hair mess it normally would unless you add supports, which we all know are nasty to get off with flexable filaments.. now you should be able to print the caps support free and not get the crap inside *( thanks to Tom Sanladerer and his live feed for the idea.) *