There are several methods for how to tighten the skin on the frame. Something close to this one was used by many seal hunters back in the day and is advocated by Brian Schulz at Capecalconkayaks. You can also stretch the cloth and secure it with tacs at the gunwhales if you like and also shrink the top deck with an iron on wet cloth. It helps if you use some kind of treated twine, preferrably 1mm tarred or waxed twine, which doesn’t slip as much while you’re zig-zagging it. In Swedish skipper terms, it’s called “nätgarn”. The PU will glue it secure anyway.
To me, this kayak is huge. I am building it to be my touring kayak and it can be loaded up maybe twice the weight and volume compared to my everyday go-to East Greenland kayak.