Maybe you could drill out the screws from the top, then push the screw shank and attached nut down into the hull where a little shaking should get them within reach. Then, stainless pop rivets to attach the new handles.
Tried that on my CD Titan I restored and found it impossible. Same piece of hardware.
I was trying to remove lifting handle hardware at front tip of the bow.
Might have a shot at the strap handle with stick method. Yes as advised above hang hull upside down . Take 1/2 wooden dowel and cable tie and gorilla tape a open end wrench to it or a socket on a small 1/4" breaker bar. Use 12 point socket or box wrench.
I hang my boats from upper deck with rope. That way I can adjust height to be comfortable when I’m standing up. Makes a huge difference in how long your patience will last not to mention your body.
You’ll need two people with a bit of mechanical skills to steady hull and remove bolt while one holds nut on inside of the hull.
Measure and mark stick on exterior where bolt is to opening then when you put it in you’ll be somewhat close and feet it.