One thing to be careful of if backing off the spring tension is that the nuts will foul the inside of the clutch case and it's not pretty if you start the bike and that happens - trust me... They can't actually be backed off that far before they do foul as they are quite deep.

What I've done is machine them to half their depth which allows them to be backed off as far as you want without them catching the case. With Barnett plates fitted, they require less tension, so a light pull can be achieved on the lever without the clutch slipping. The only pain with the Bultaco is that adjustment can only be done with the cover off, so if you back them off too much and then find it slips, the cover has to come off again. I generally set mine by riding it around the garden with the cover off before fitting it all together.

what about the security wire holes woody?

A useful tip for setting the clutch spring preload:

Fit the plates and pressure plate with a coating of oil on them

Set the free play for the push rod

Set the clutch spring preload so that there is just enough drive through the clutch that you can kick it over compression with the kickstart without the clutch slipping

That will get it very close to perfect before you take it for a cover-less test ride. The last two bikes I did, did not require any further adjustment after using the kickstart test method to set the spring preload (M49 Sherpa T with Barnett plates and M138 (350) Alpina with Bultaco plates)

what about the security wire holes woody?

They're gone as I machine them down to them. Never had a nut come undone so it's never been an issue, although it should be possible to drill new holes in what's left of the nuts, just in a different position