I've used carbon-fiber reinforcement fore and aft of the cockpit on both strippers I've made for the extra strength and stiffness. Kevlar, although "bullet" proof is not the cloth of choice for this type of reinforcement since it's not as stiff. Put the carbon fiber strips on after glassing the inside deck, the weave perpendicular/parallel to the strips for greatest strength. On my latest project, I also put carbon fiber triangles under the cockpit area where I press up with my knees for bracing. Carbon is nice for hatch lip fabrication but multiple layers of 4 or 6 oz.glass cloth will work fine. I really like Vaclav's approach to hatch lip fabrication.