It's almost impossible to build a stripper that leaks if you follow even the most basic building method.

Check for loose hatch covers (with no bulkheads) and loose sloppy fitting spray skirt. Just sit in the boat bone dry in the water and see if it still takes on water. (no paddling)

Check where you drilled holes for a carrying handle. Are they in solid material? If you have water tight bulkheads you can rule out the hatch covers and carrying holes.