I would strongly recommend that instead of trying to "figure it out," particularly by using just one book, you do more research. One of the places I think you should look before you start the project is H. C. Petersen's Instruction in Kayak Building. If it were me, I'd scrap all of the plans and measurement systems from Cunningham and build from Petersen's book, and use Cunningham's book as a reference for how to build it as far as using tools and such. The design parameters in Petersen are MUCH better. Follow them TO THE T, EVEN IF THEY DON'T MAKE SENSE- as you build it will become apparent how it works. Also- be aware that Cunningham's book is jig-happy. You will spend forever building jigs and buying lots of scrap wood to make them with, and not much time building a kayak. If you want a more (much much more) pragmatic view of tool use and "how-to" you should look at Mark Starr's book Building the Greenland Kayak.

Also- as far as figuring out ANYTHING, whether deck beam placement or rib placement, it is best to look at actual examples, not just go by what Cunningham says. It's only a tiny view of a subject that has wide variation. You really need to pick up Harvey Golden's Kayaks of Greenland. Once you look at 10-20 kayak surveys you won't have questions about where to put deck beams. Harvey has a web site that has SOME drawings, and SOME build logs, but lots of photos of finished kayaks at: http://www.traditionalkayaks.com

I would also very strongly suggest she read the writings of Ken Taylor, who spent time living in Greenland in the late 1950s and becoming immersed in the culture. One of the most famous kayaks- the 1959 "Ken Taylor" which was built for him while in Greenland was the basis for almost all of the "Brit boats" like the Anas Acuta, Nordkapp, Avocet, Greenlander, Romany, Explorer... He has been spending a lot of time over the past couple of years documenting his experiences. One of the chapters is about kayak design. https://kayakgreenland1959.wordpress.com/2015/07/22/chapter-six-variations-in-kayak-design-2/

You may also want to peruse QajaqUSA.org.

I guess the bottom line is that if you are using Cunningham and think a deck beam goes somewhere, and you're not sure where to move it if you "stretch" it, you're probably doing the project the wrong way. So- don't commit to anything until you do some more research. It's more a lack of background information than a lack of specific information. Trust me. I made many many mistakes on my first kayak... Back then Morris was the only book available in this country, Kayaks of Greenland hadn't been published yet, Qajaq USA was just getting off the ground, and I had never seen a SOF kayak before. None of those are issues now. You can read the details of my mis-steps and get some information on how to avoid them here: http://www.qajaqusa.org/newsletter/Masik_Spring-Summer_2008_v8.pdf

Lastly- she may want to consider building a replica. I have given up "designing" my own kayaks and build replicas, but that's partly because I want to know what those kayaks paddled like more than I want to try and reinvent the wheel by putting something together on my own.

m