Yes, you're right - It's 3/4 at the grab loop with a taper to 1/8 at the bottom.

What I'm doing is trying to avoid those sharp, thin and pointy ends that is common in wood kayaks. It's an artistic call more than engineering. Commercially made boats have a thickness at the grab loop point that visually gives a solidity to the craft. This is what I'm trying to achieve. You could go for thin ends to your boat but I believe these small details, which really don't take much effort add up and make a decisive difference in the look.

You want at least an eighth, so you have surface to glue on your external stem pieces. The other thing you can do after the hull is stripped is grind a bit of material away and expose more thickness. Since you're new it's confusing but once you do it you'll find there's a million ways to do things. Sorry if I created any confusion. I would go with the 3/4 to 1/8 taper ... and don't wory about it. As long as you get a taper it will look good. You will carve it thin below the water line with the external stem material so it slices through the water nicely.