People with less experience generally have to do what is safest for them to do.

Here is a story about different peoples capabilities

I worked at a place where we worked stationary Diesel Engines. Larger then vehicle engines. We would get the new Cylinder head from the one engine (each cylinder head covered 2 cylinder) came in a wooden crate that was about 3 feet 6 inches square made of thick wood. The nails in the wooden crate went in about 3 inches and there was a lot of them and you could work up a sweat using a hammer and crow bar to take the crate apart to get the head out.

We had one Guy in our shop that would grab the corner of the crate with one hand and soon you would here the creeking sound of the Nails loosening and slowly he pulled the lid of the crate right off. Once the lid was off he easily took apart the rest by hand. He was the only one out of 16 of us that could do that.

He lived up to your member name hercules.

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84 300D, 82 Volvo 244Gl Diesel

Strange this has never seemed an issue before. I even thought the adjustable length was just to cover various manufacturing tollerances.

The Centering Pin on each end of the Drive Shaft stick into the Centering Bearing more then one inch. Hercules claims with enough force you can move the shaft that much and get it apart because he has more experience.

If I have to do work on mine I am going to continue to loosen the Coupling Nut and collapse the drive shaft so I don't have to force it to get clearance to get it apart. But, that is my personal choice.

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84 300D, 82 Volvo 244Gl Diesel

I was concerned more with the aspect. If the coupling nut has to be loose somewhat to get rid of a vibration. Where I thought by design the spline that allows length adjustments.Was just to cover manufactures parts tollerances.

It almost sounds to me that the poster with the issue somehow had the driveshaft a little longer than it should have been somehow. When he initially locked it down. This might occur if you were using your wrenches to tighten the coupling with a vertical force component. The tightning force is perhaps applied better in a hoizontal direction.

Pre lockdown the spline slide should be pretty free moving. As for removal of the driveshaft I have always used the reduction of length approach.

The only thing to be said for what the poster of not using the slip ability did. The past driveline length is preserved. It just sounds like a royal pain to deal with the Driveshaft in that fashion.

My observation is that the yoke with the splines on it is extremely hard and I learned that when marked it with tungsten carbide scribe which took a lot of effort to get mark on it. (not I did not rely on those cast factory marks I match marked both the collar nut end and the yoke end.)

On the other hand the part that the collar nut squeezes seemed to be soft and springy and I easily used a center punch and punched a mark on it.
That make me think that tightening it could warp it.

Also we don't know if the splines inside were worn as some have had happen.

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84 300D, 82 Volvo 244Gl Diesel