Maiden ride on my Z1B highlighted extremely hard front end and screeching noise on large bumps

. Stripped forks and found springs that measure 507mm long, last 60mm of coils with no clearance, outside of coils are polished so I think thats the screeching noise as they compress and rub on the stanchions. Forks are also topping out on large bumps as the wheel drops in. Manual says springs should be 495mm long and constant coil. I think mine are from a Z thou, again manual says 511 mm long but with age they could have compressed.
Static sag is 23mm, riding along and braking etc only gives 76mm movement inc static sag, our kids Z1B forks static sag 29 mm and move 105mm inc static sag when riding.
Had my shoulder joint replaced so need front end thats absorbs bumps, its very uncomfortable as it is, softer front would reduce jarring, plus as is, its almost unrideable on local Cumbrian B roads

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Anyone know where I can get some standard fork springs?
Jeff @ Z1 Enterpises says he can supply progressive springs, anyone used these- feedback please.
AKA John Roscoe. PUM #028
1975 Z1B, 2013 Z800