As gunner, I have not found these drain plugs to be a common leak site, and I've never had to resort to Teflon tape or sealer. Just snug it down with a proper washer. I've even had plastic washers work, but fiber, copper, or dowdy (best choice IMO) are more durable.

Mark Z

'65(lower)/'66(upper, wheels, front end, controls)/'67(seat, exhaust, fuel tank, headlamp)/'70(frame) A65 Bitsa.