You really should get the rear wheel/tyre in swing am and the shocks your going to use before welding rear hoop.
I always fit shock without spring to see where the wheel is going to end up, usually higher than you expect.
I don't know how a piece of piston ring could go through oil pump, through filter, up oil passage and into cam bearing?
If it went up with cam chain, it would leave marks, plus, it would be more likely to damage other stuff.
You want to strip oil pump and check it, damage on main bearings and cam bearings shows something was wrong somewhere?
You really need to check con rod on the piston that is beat up, if big end is damaged, the rod could be close to stress failure?
I'm going to read some more and make comments later ;D
Piston failed because of constant over revving, probably from cold
There was probably a very slight pick up between piston and bore, ring caught on it and started vibrating up and down in ring groove. (you can see lands got mushroomed enough to be rubbing on cylinder walls)
Was it #3 cylinder? (#3 seems to be an issue on most Honda's when things go wrong
)