I would not be concerned about Nida-core I have built over one hundred boats out of it. Though not as strong in shear as some foam cores, it does not fail catastrophically like cross linked foams, since the polypropylene honeycomb will deform or bend first, it has great peel strength because the thermally fused polyester scrim creates a good physical bond to laminates, acoustically it is vastly superior to other cores, and it costs less. It will make for a heavier laminate than some foam cores, since the scrim absorbs some resin, and it is not as stiff in shear compared to some foam cores, so laminates would need to be thicker for a given panel strength. It is unaffected by water, and I have seen water drained out of the core in some cases without affecting the laminate. The first seventy five Manta's were built entirely, hull, deck, and bulkheads out of Nida-core and polyester resin, and they are all going strong. IF price was not an object and/or I was building a race boat I would maybe look to other cores and epoxy resins. On the subject of ground affect or air cushion I would be hesitant to say emphatically that no benefit is gained under 25 knots. It has been my experience that it can help at lower speeds than that.