I started using balsa for only the main decks, it was much easier to cut and simply does not warp like heavy card stock. It was so much easier to cut and sand that I just started using it for the bulk heads as well. You have to be carefull glue the decks in place as white glue is still the best way to glue the paper to balsa. I pour the white glue into a small bowl the spread it with a 2 inch paint brush. The deck card stock is usually heavy enough not the stretch or bubble as the white glue tries to expand the paper. For the thin sheet bulk head patterns I use a glue stick that dries fast enough not to cause the paper to stretch. It just does not have the holding power so it tends to peel. I then just touch up the edges with CA. The entire frame is fitted then little by little I dab CA into the slots.
The nice adder is the model weight is much lower and handling is easier.
As far as the gaps, this is not so untypical of the older kits. Some guys make their own by laying grid paper over the bulk heads then tracing the needed shape. I time consuming process I will try someday.
I like the idea of the foam, I don't have any tools for it but it looks good. For this model the edges would still not match on the paper plates even if layed over foam.
I think the hull will look once I paint it. The upper hull sides went on very easily and smoothly.
Back to another paint coat on the kitchen and time allowing I will put the 3 starboard plates on tonight after the Kitchen work.