Consider 2" unidirectional carbon tape from J.R.Sweet. But make sure it's absolutely necessary, I'd check with Nick. The stuff has fundamentally different failure characteristics than wood/glass . If there's a bulkhead behind the coaming the issue is moot. Likewise a thin transverse stiffener of wood with a layer of glass over it for the hatch areas would cost nothing for the same effect. This isn't to say I haven't slathered some boats with pricey cloth. It's just that usually the "extra" whatever needed can usually be achieved with 1/2 square foot of extra 4oz and a little structural stringer. In superlight construction I could imagine a broad latticework of 1/4" wide carbon strips under the back side with 4oz s-glass but this is getting kind of obbsessive and a waste if the entire construction isn't superlight.