My observations regarding top bar hives are favourable. It seems to me easier
to control pests and diseases since one can simply cut away the comb and give
them new foundation very readily.

If the bees have a predisposition to cluster the brood in the center of the
comb as suggested by the earlier respondant, one can simple keep replacing
the last brood top bar with a honey top bar. Eventually the brood patterns
will change. Another more permanant way to deal with this would be to build
the hive narrower and longer than ordinary. Perhaps instead of a hive that is
19" wide and 12" deep, build a hive that is 14" inches wide and 10 " deep and
add enough additional length to replace the missing comb. The clustering
brood bees will be forced to use most of the brood comb for brood and pollen.
TBHs are extremely versitile and you can design hives for any specification
that seems necessary.

I am a great advocate of the TBH and I find it ultimately much easier to
handle and manage the hives. One of the important considerations is designing
the hive to meet the requirement of the bees within your climate