As a would-be beekeeper, I really like the idea of catching swarms (free bees, feral genetics, fishing for bees... just plain interesting stuff, etc.)
While I have conventional Langstroth equipment for the nucs I'm getting in the spring, I'm also fascinated by top bar hives. So the traps I've started building have top bars rather than frames.
I like the idea of Tanzanian TBHs because of the interchangeability with conventional equipment, if you make the top bars 19". According to Michael Bush, I should be making the TBH of medium depth. But when I built a swarm trap with those measurement, and of 40 liter volume, I ended up making a whole lot of top bars, which seems counter to the idea of making up a few quick swarm traps. Anyway, 40 liters makes a wide shallow swarm trap.
Is there any good reason not to arrange the 40 liter volume in a vertical form? To put it anther way, the box would have its longest dimension up and down, kind of shaped like a pack of cigarettes. I'd only need 5 or so top bars per trap across the top. A disadvantage would be that if I forgot about the trap for a month or two, a swarm might build combs over a foot long, but even then, I guess it wouldn't be as bad as a cutout.
The vertical form would be easier to mount in a stable manner, too.