<<<#1 At 1000 feet per minute of piston travel, or 4000 RPM  the rings on
the piston can begin to vibrate. or resonate.  The wear would be to
pound out the groove the keeps the ring in its place on the piston...>>>

Why you want to use HIGH quality parts...

<<<#2  The  other high rpm issue is the crankshaft.  Whether 1.9 or 2.1
WBX, there seems to be a concern of  wear on the center crankshaft
bearing surface.  This wear is attributed to the crankshaft flexing in
the middle, ends stay put. The effect is to elongater the center bearing.>>>

WHY I COUNTERWEIGHTED the crank!  TO Keep the crank from flexing, reducing bearing wear increasing strength of the crank, increasing power, keeping the rods at correct 90 degree angle to the crank, maintaining correct oil film on crank, etc.

It also enabled me to lighten the flywheel to improve acceleration...

It revs to the redline quickly and is smooth as glass...
The RPM range of the engine is 1500 to 5800, which is with the five speed gearbox a mph from ~25 to 80 in fourth and 35 to 90+ in fifth...

Robert