'Otter'. Build log.

[Voicecoil]

There's a really useful motor/ballscrew calculator spreadsheet somewhere on this forum which I found really useful, though I can't seem to find it at the mo. - worth digging out and putting in your predicted mass/lengths/desired speed to see what motor/power supply suits.
On the subject of steel tubes I stumbled across this last week whilst looking for something else:
https://www.barrettsteel.com/product...recision-tube/
other vendors seem to do similar products, it appears that the straightness spec. is better than normal stuff.