The Day Sailer and the Javelin used the same rudder, my 1979 DS II has a hole drilled in the top pintle, they came from the factory this way. Does your boat have a replacement rudder? My rudder is mostly solid fiberglass and has never lifted out of the gudgeons while sailing, good thing since it would sink fast. We used to have a larger sailboat with a solid mahogany rudder and on htat boat you HAD to insert a pin into the top pintle, otherwise the rudder could (and definitely WOULD!) float off the pintles while sailing!
Drilling a stainless-steel pintle for a pin is not impossible, but will require a sharp bit! It might be easier (not as cheap, but) to buy a replacement pintle from D&R, Rudy sells them pre-drilled and with a safety pin.
www.drmarine.com