[Vwdiesel] More Quantum questions?

[William J Toensing]

In attempting to clean  rust off the flywheel,  I accidentally erased the "O" TDC mark on my flywheel. Is there a way to find & mark TDC on my flywheel without removing the head to see when the #1 piston is at maximum height? In attempting to re-time my engine I apparently moved the timming off enough so that when I turn the engine over by hand, either clock wise or contra clockwise, a piston hits a valve & you can't turn the engine further. I have not tried to force it. I wonder if I could find TDC by marking on the IP gear how far in either direction I could go till I hit a valve with a piston, & mark TDC as half ways between these two points? Or is TDC more than or less than half way between these two points? I just checked & there are four gear points between the point where the piston hits a valve. 
My suggestion would be to mark in a more permanent manor such as drilling a small hole at TDC before doing any timming adjustments on the engine. If I am wrong, please correct me.
Bill Toensing, Nevada City, CA