I've heard people express concern about heat build up in the compartments if your kayak is left cartopped in high temps, however, I've neither read nor heard of any actual problems arising from lack of hatches. I think you're safe.

: I have just completed a CLC West River 164, during construction I decided not
: to cut hatches into the deck so cosequently the fore & aft
: compartments are sealed, is this a problem?