My cassettes are always flapping about on the freehub because I've never got the guts to do them up very tight, as that klunk..klunk..klunk sensation as you do it up makes me feel a bit sick, so I normally stop at 2 or 3 klunks.

What is causing the klunk? Is it something horrible happening to the pawls on the ratchet, or something harmless and just ignore it and keep tightening?

I see the recommended torque on the lockring is 40nm, which is quite a bit, certainly way more than I ever give it ? (I don't have a torque wrench that goes up that high unfortunately).

there are serrations on the surfaces of the cassette and lockring – I do them up very tight – foot long spanner plenty of effort tight. Probably rather more than 40 nm 😳

Assuming it a standard hub/cassette eg. not 8 speed cassette on a 9 speed hub just tighten it until it stops klunking and is 'snugly tight'. You won't be anywhere near the pawls.

Just remember, you will probably have to get it off at some point too!

as woody implied tight enough to stay on – loose enough to take off would be my line of thought but…
was doing one today and after hearing it "crack" a bit but no effort got out the torque wrench and guess TJ is right big lever job – think its hard to nip them up tight because even if get chain whip right it is still a bit of a wrestle hard to guess

theres only about 5 threads so be careful. i usually go to just under 40nm.