Soft spots can be failed lamination or a failure in the actual foam core sheet. Years ago this foam was sliced from large cakes or "bread loafs" of foam. Density and materials mix could vary depending on the area of the bread loaf a foam sheet was cut from. Some soft spots may be caused by this marginal foam or possibly dry lamination. These boats may not handle harsh conditions. Seems there is a higher proportion (from memory) in Texas. Hot conditions and humid conditions may play a role. Keep it dry and cool if possible when in storage. Do not use a dark colored cover for storage. Keep the plugs out and hatches off, but do not allow rain into the ports. Also a good idea when traveling. Be sure the hull vents when sailing. A hull that is too well sealed will have negative pressure in cool water and high pressure inside when heated sitting on a beach. This flexing of the materials is a problem. Another cause is compression on a hull surface. This can compress the foam or fail the lamination over time. You can see that more commonly in a Hobie 16 deck just ahead of the forward pylon. This is a high stress area that is also a step people use getting on and off of the boat. Also areas of the hull that are walked on (decks and sides while righting).