I did almost what you did. I still have my two modifies screw drivers. One for cutting along the sides ( after going thru some razor knives) which was easier due to the nice grip provided. Then modified other bent 90 degrees and ground and sharpened to fit the grooves. Cleaned area with MEK and caulked. My advise is spend money and buy a battery powered caulking gun. I did my entire 37" NanTai (Ta Shing Yard) turned out well. Still had leak in aft head and after 8 years of trying gave up. Teak was beautiful, but never again. Iceman