The crank case locking pin hole is used when working on the engine to hold the crank shaft in the top dead center position. You remove the hole plug and screw in the crank case locking pin which goes down into a hole in the crank shaft when the crank is alligned at TDC. It essentially bolts the crank to the case allowing you to set the cam sprockets, etc. If you use it for an oil return line it would work great and the line could be removed anytime you needed to use the crank pin.
It's not how fast you go, it's how fast you get there!