Extend 22mm solid driveline by about 200mm

[68Charger]

Sounds like you've got a plan now. Glad I was able to help. You know when I first saw metric numbers in the post title, I almost didn't open and read it. Metric? You Commie!

I have done enough work on AKs that I'm used to using Metric for mild machine work (pin sizes are metric, etc)... I supposed I could have said the shaft is .866" in diameter, and I need to extend it about 8"... and a Commie wouldn't be looking at buying a 1.25" x 3/16" wall tube to extend a metric part...

If it were me, and it was going to be cutting/welding anyways, I'd probably just cut the ends off the old shaft and make a new shaft end to end instead of splicing the old one.

But, I'm a bit OCD that way.

If you're re-using the ends, aren't you splicing it anyway?

This shaft is not like a car/truck driveshaft- it's solid, and has splines on each end- the U joints fit over the splines, there are not ears welded on a tube like a auto driveshaft.
I could make a new shaft but that would mean machining the splines- that would be more work than splicing the shaft...
I have a small mill, but no lathe With a rotary fixture and a key cutter, it could be possible to machine the splines- I guess that's a fall back plan if the splicing fails