[SFfiredog]

Simon,
Please check your bearing clearance at the fillet (cheek) of the crankshaft. Aftermarket cranks have very generous fillets, usually .125" If you used standard rod bearings without chamfering the bearing end at the fillet, the side to side clearance
on your con rods is next to nil. This clearance is critical to oiling the cylinder walls. I have seen this problem before.
Also, how cold did the engine run. I've seen wear patterns like that from engine temps that we too low causing too tight pistion to wall clearance when under a load.
Good luck,
Mike