I have an old fiberglass tandem kayak that needs a rudder. The top
and bottom were attached with a flat external seam. The top is
somewhat peaked and not flat. I cannot tell it the ends were poured
because of foam flotation that has been installed. The stern has a
small flat surface about 5 inches high by about 1.5 inches and I want
to mount a bracket shaped like this [ to the stern for the pivot pin.
My question is about attaching the bracket. I need suggestions.

If the end is poured, can I drill it out and use machine or wood
screws that will self thread?
Should I use a lead insert like a concrete anchor?

I cannot get at it to use a nut and bolt. and I do not want to drill
exploratory holes if I do not have to.

This link will give you a visual or what I am talking about....

http://www.oneoceankayaks.com/Wslrghtm/jpg26/S26-1.htm

Any other fasteners or suggestions would be appreciated. If you can,
please reply by e-mail also.