Simon, oh no, not again!
Some thoughts:
1: Are the side-to-side clearances right on the big ends? Cylinder lubrication comes mainly from splash from
oil coming out of the big end bearings - too little clearance between the two conrods on each crank throw can reduce this significantly.
If this is the cause, I think you may also find a small end gone bad somewhere - your knock.
2: The piston scuffing could also be from too little piston-cylinder clearance. It could be that although you had the bores sized right, you have the WRONG pistons. Measure some of them, assuming you can find one or two that are not badly scuffed, and mike the bores to see what ACTUAL clearance you have.
3: The loose rocker episode is a red herring - it did NOT cause the damage you are now seeing. Forget about it as a cause.
4: Did you have any signs of severe overheating? Running-on after turning off, pinking etc?
5: I am still not sure that your knock is coming from these pistons - piston slap varies greatly with engine temp. Did the knock change at all as the engine warmed through from stone cold?
6: Tell me EXACTLY what ring gap you set. Ring gaps are often quoted as so many thou per inch bore diameter - you have to multiply the stated figure by the bore dia in inches.
HTH
WIlf
PS - Anglo-American translations:
small end - wrist pin and bearing.
big end - big end or rod bearing
pinking - pre-ignition or pinging
