Don't think I recall anyone on the forum who has actually used em. Maybe you'll be the first. What IS the cost???
Perhaps a different approach...
You say the stringers are bad only at the top. If that's true, perhaps you could cut off the top inch or two using a circle and reciprocating saw. This would give you a flat surface of good wood to glue and screw another piece of appropriate wood onto to bring them back to their original height. Think 1 x 2, maybe hardwood. You could then rough and clean up the sides with a belt sander and glass some plywood onto the sides for extra strength.
The stringers might only be "bad" at the top, but if they are rotting at the top, I can almost guarantee that they are waterlogged a fair bit farther down. Glue doesn't stick well to wet wood... And it's only a matter of time before the rest of the stringer gets "bad". The solution is to get all of the compromised wood out, and replace it with something new. Most people here use all new wood, because it works well, and costs less than the other options.
They work fine, but are pricy, so not many people use them.
Deck putty, is just putty, you can make it or buy it
You would normally glass over the plywood and tab it to the hull, nothing out of the ordinary there.
Perhaps a different approach...
You say the stringers are bad only at the top. If that's true, perhaps you could cut off the top inch or two using a circle and reciprocating saw. This would give you a flat surface of good wood to glue and screw another piece of appropriate wood onto to bring them back to their original height. Think 1 x 2, maybe hardwood. You could then rough and clean up the sides with a belt sander and glass some plywood onto the sides for extra strength.
I was reviewing another forum and this same idea was mentioned as well.
I did find one idea that I am liking problem is I know it will add a bit more weight to the boat. I'm see where guys who have had to start over like me have gone through and added bulkheads to give more strength to the deck. This might be something I explore further.
Nothing failed in the original design, even after the wood started to rot, so what are you going to gain by redesigning it.
You seem to be overthinking this project, just rebuild it the way it was and it will be fine for a few more decades.