I'd say 1" is too wide yeah, but I don't know if it would effect you
0.75 is more than enough. Some say it may have been thinner. A cm....but.........
One thing I will say is, back in 76, a metric measurement on anything in the UK would have been very rare. Everything was imperial.
My mate, who loves his engineering and the golden olden days, laser scanned my Sterling and was impressed there are no metric measurements on a Sterling All imperial lol
Good on you for that detail as a lot use the wrong blaster even