Your right. Iassumed you were referring to the entire length of a top bar hive. For me, that would have required a several pieces framed or one long piece 48" long minus the associated framing.
Yours would be ok.
Since I was mainly interested in viewing the brood nest, I kept the viewing area to the front with the second window for illumination mainly.
I don't know how successful the design will be until next fall. I just know this is what I had been looking for. Now if only the bees will concur