I can tell you all this: I can wash the entire cockpit with a running hose, tilt the boat up to drain and the bilge remains 99+% dry. It's possible that water can leak down via the side wall storage boxes, which are not sealed off. But these hatches make a huge difference. Make sure the sealing surface is clean before you close them, as grit seems to find its way in there.
That back joint looks similar to mine, since the hatches don't have "hinges" and snap into the frame at the rear. Remember, if you cut out the hole to the correct size, the back frame will be parallel to the front more as it won't flex out as much.
FWIW, I used 4000 as that's what I had. I also completely sealed off the balsa with thickened West Systems epoxy, even every screw hole.
That back joint looks similar to mine, since the hatches don't have "hinges" and snap into the frame at the rear. Remember, if you cut out the hole to the correct size, the back frame will be parallel to the front more as it won't flex out as much.
FWIW, I used 4000 as that's what I had. I also completely sealed off the balsa with thickened West Systems epoxy, even every screw hole.