ok, i just did a quick experiment.. and it was as i though. the piece i tried as probably at the most, 5/16 at the thick end. the only dowel i had on hand was 3/16's and i had to file it, but it served its purpose in my test. since the cut will be in the middle it will affect the total spine. but... im very tempted to test the shaft out. since youve essentially created two very stiff shafts with a very flexible joint.
i can imagine, if you wanted to do this, find the thickest usable cane diameter you can use, then, get the biggest piece of dowel you can safely shove in there and try it out. it will have to fit tight. i really need to get the proper drill bits to match the dowels, i have a drill bit that is smaller than 3/16s, so i have to shave the dowel down a bit..
definitely dont miss. probably wasnt a good idea to shoot it in the dark, first arrow shot in a couple weeks.. but i missed, unfortunately i wont get to shoot it again, because the dowel broke.
definitely get the biggest dowel in there as possible..