I just had a very similar experience on my H17. My soft spot was from a misplaced foot between the center board and the rear cross bar. I thought it was a classic soft spot from delamination. I tried to fix the spot by drilling the holes and injecting resin. This just didn’t work. I couldn’t get the resin to even go in the holes. I finally installed an access port in the center of the soft spot. When I examined the piece of decking I removed in installing the port I found that the inner fiber glass layer had split. I repaired the crack by applying 3 or 4 layers of fiber glass.
That is exactly what just happened to me. I went out today drilled the holes and nothing would go in. One hole though had no glass on the bottom side. My drill went from foam to air. I am convinced the inner skin is ruptured.
I have the access ports to install. I will In stall them this weekend. I am going to try something different involving strips of teak.
Frank, sailing '02 Getaway in Wichita KS. Lake Cheney
(Hobie 17 RIP, storm of '05)