With LITTLE experence with a TBH. I built one quickly (too many swarms) so far I like the results. Not knowing much at the time; I cut 1 3/8" bars X 19" with a 1/8"+ saw kerf, poured in bee wax, then took a light saw cut to clean-up excess wax. So far the comb is nice and stright with good attachment. I am making a couple more TBH's, but the bars will be 1" wide and with a triangle cut bottom section and use 3/8" spacers.
There is a earlier post "Photos of my TBH", great photos!
Take a good look at the "starter strip", the comb is attached to the strip and the strip is attached to the bar.
My observation is: that strip better be will anchored and of a stout material
