Ah, solid core or massive core composite. I haven't seen his site, but I am familiar with the method.
One of my favorite sayings,
Soloman wrote:
There is nothing new under the sun.
For me, that means that anything I can think up, has already been done, and I just need to find who did it and adapt from there
His tutorial page for his massive core outrigger had a maximum width of 6". (he used 3" on each side of his web)
My largest bulkhead is, 17.71" wide by 15.81" high, so significantly more volume, mine wont be training wheels, they will be big enough that a smaller person could probably sail it as a catamaran without the canoe attached in the middle. (over 400lbs of buoyancy per hull)
I am familiar with stitch n glue, so there is no learning curve for me, that directed most of my decision process. I wanted it to be a quick (hopefully) project, not a time to learn new construction methods, even though I am with the mast and beams etc.....
If this was a serious endeavor, or for an aircraft, there are calculations you run at which point the weight advantages for cored composite vs massive core swap based on volume and shape. For a very thin structure, massive core wins out because you only need glass around the outside, so you have a layer of glass on each side of the surface, lets call it top and bottom, for 2 layers. For a thin cored structure the same dimensions, you would need 4 layers of glass(or carbon or kevlar or whatever you are specing...) Glass and epoxy weigh a lot more than wood or foam. So you need to run the numbers to see what your 4 layers of glass/epoxy + 2 layers of core weigh vs your 1 massive core and 2 layers of glass/epoxy.
Because I am using wood not foam it would tip more towards the massive foam core, however as large as my volume is, I am guessing it would still tip in favor of the thin core in terms of weight for the size cross section I am working with.
I find the study fascinating, and wish I had the time to run more numbers on it instead of just theory from memory, but I am already taking time away from other projects to do this, so trying to stay as simple as I can