Got it out and the damage is indeed as many have shown. I'll add a picture later but nothing new. We are at a latitude where AC in the summer is a must and the damage was done over many years I guess. The spline engagement is pitiful.....

I am going to order the spline shaft and the spacer (found the listing last night). Once I get the parts I will cut the drive shaft and put a hose clamp where I think the maximum length is. Then do a mock install to check that I can get the parts in to place at the new maximum length. Max length should be 30 1/8 minus about 5/8 for the spacer. So, the shaft should be at 29 1/2" when welded together. That should leave adequate space to install without undoing the TC as Eskirvin posted.

Now off the "fastener store" to find 15mm longer bolts for the flex disc. Also need to swing by a local trusted indy to find out if they have a recommendation for a welder.

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2003 4.4i black ext./black int./black headliner (kid's runabout)
2014 535d X-drive, M package, silver/black interior

Sold but not forgotten:
2009 E70 35d, black ext./black int./black headliner (sold 2021)
2006 4.8iS Le Mans blue/cream int./black headliner, SOLD in 2012 sadly...

Other hardware:
2015 Cayenne S (wife's new DD and definitely wroooommmmm)
2016 Tundra 1794 edition crew cab, luxo hauler
2005 Tundra crew cab, weekend hauler. Sold after 150k very happy miles.