Just trying to think like a bee! (LOL) It's like my first attempt at logging with draft horses. I had an older mare that had some logging experience. I had none. Any horses I had driven for haying, etc., would just step straight out. No matter how hard I tried to drive this old mare straight once we hooked onto a log, she'd always take a a few steps sideways then go straight......figure it out yet. She was trying to teach me something. If she broke it loose first by pulling sideways, she could get it started easier and off we'd go! She could out pull most teams!
Anyway, since I'm just building the TTBH, wouldn't be any problem to put top bar supports from side to side so I can rest three sets of top bars parallel to the long sides. A potential problem I thought of was they would ignore the space created by the supports and just build 4 foot long comb. If I could just figure out a way to interrupt the long comb.....then they could keep building the way they like, and I could do beekeeping the way I like!