Thank you Maple Leaf!
Rest assured that it cost me a considerable amount of sleep before I decided to convert the rifle. It was a decent shooter but not good enough to compete in a match, my older No.I Mk.III performs better. The damage is minimal and invisible however, a small pin welded just in front of the chamber to prevent chambering a live round, but blanks will fit.
My favorite gunsmith drilled and tapped the rifle with the prescribed tooling and the pads fit nicely. He said the only way he did not follow original procedures was the use of Loctite instead of solder and not staking the screws.

I'm pretty sure that a couple of fellow hobbyists will absolutely scrutinize the work done, on the other hand I feel confident that it will prove worthy of showing. And that's better than storing a fine rifle for nearly 100% of its existence in a locker.

After reading the link it is clear to me that no additional marks are needed on my rifle except for possibly the scope number on the butt. I have no problem with a mint looking replica Mk 1 scope on the rifle because the rifle itself is still looking very decent.

Still a question considering the leather case strap. 60" suggests a considerable excess length for only securing both halves. The canvas Mk 2 case also has carrying straps. I just flipped through the book of David B. Gordon, Weapons of the WWII Tommy and saw both items pictured, the steel case with an indeed quite lengthy strap. Like you said provisioned for but practically seldomly used...

Regards,
Theo