My original idea was to drill guide holes for long screws, attatched to knobs like you would have on a drawer or something, but I couldn't find any knobs with screws long enough to go through the thickness of my end piece and far enough into the poles to stay put, plus, eventually with the screwing and unscrewing it would wreck the wood in the pole.
With the dowels, I'm thinking of drilling tiny holes through the ends that stick out past my end piece, and put a small rigid wire through all three ends to keep the tension. Like the thickness and rigidity of a metal coat hanger.
I like the price of the one mentioned from allbrands, but I dont understand how to adapt it so I can put bigger quilts on the frame... maybe I'm having a blonde moment and it's just not clicking in my head, lol, maybe someone else can fill me in?