TRactor By Pass

My apologies, folks, for asking a chestnut question.

I've put a dowel plug in the thermostat bypass of my TR3A engine rebuild.  But
it niggles at me that I was supposed to drill a quarter-size hole in the plug
to allow some water to relief bypass.  Which of me is right?

Terry Smith '59 TR3A  (Body off, rest mostly back on; awaiting body guy!)
New Hampshire